Practical Sanitary Science - Forgotten Books

PRACT ICAL

SAN ITARY SC IEN CE

A HANDBOOK FOR THE PUBLIC

HEALTH LABORATORY

DAVID SOMMERVILLE

B .A M .sc. , M .D . , D .P .H . F.C .S .

ASSISTANT- PROFESSOR OF HYGIENE AND PUBLIC HEALTH,W ITH CHARGE OF THE LABORATORIES

OF HYGIENIC CHEMISTRY AND PHYSICS,UNIVERSITY OF LONDON KING ’ S COLLEGE ; EXAM INER

IN BACTERIOLOGY AND CHEMISTRY , B .SC . ( PUBLIC HEALTH ) , UNIVERSITY OF GLASGOW ;EXAMINER IN UNIVERSITY OF ABERDEEN ; MEDICA L OFFICER OF HEALTH ,HARROW ; LATE DEMONSTRATOR OF PHY SIOLOGY IN THE MEDICAL SCHOOL

OF ST . THOMAS ’ S HOSPITAL

SECOND EDITION

N EW Y O R K

W I L L I AM W O O D C O M PA N Y

MDCCCCXV

PREFACE

TO

THE S ECOND ED I T ION

THE arrangement in chapters has been altered , and con

siderable additi onal matter has been added .

The introductionto qualitative chemical analysis has

been discarded in order to prevent increase in size of the

book .

Som e less frequently occurring Operations are outlined

, in a brief appendix .

D . 8.

UNIVERSITY OF LONDON KING’S COLLEGE,November , 19 14 .

PREFACE TO THE F IRST ED I T ION

THIS li ttle book is a brief summary Of the course Of practi cal

lecture - demonstrations given to the D .P.H . class at King’s College ,

London . Its i ntention i s to put in the hands of students working

in laboratori es of Public Health a short outline Of the more

important matters—chemical , physical , etc .— d i scussed at practical

examinations in Sanitary Science .

The methods described are few , but it i s hoped they will be found

reliable . I t is felt that where a large field must be cultivated in a

limited time , i t i s better to use a few tools which have been well

tried . Whilst going through the work , the student will do well to

constantly refer to elementary up- to - date textbooks in the sub j ects

O f experimental physics , systematic Organic and inorganic chemistry ,

analytical chemistry , geology , and bacteriology . Further , i t wil l

be necessary for him at the outset to bear i n mind that no amount

of theoretical reading can be made a substitute for the laborious

and constant use of the test - tube , microscope , etc . , which must

take place at the benches .

A short account Of the preparation Of the standard solutions

referred to in the work , and a few brief notes on the general

chemical reactions of the more commonly occurring metals and

acids , are set out in an appendix .

D . S .

KING’S COLLEGE ,

N ovember , 1905 .

C O N T E N T S

CHAPTER PAGE“

I .

“

GENERAL OB SERVATIONS UPON POTAB LE WATERS I N RELATION TOTHEIR SOURCE ,

AND METHODS OF EXAMINATIONADOPTED FOR SAFEGUARDING THEIR PURI

’

I‘

Y

PHY SICAL EXAM INATION OF WATERI I If THE CHEMICAL EXAMINATION OF WATERIV . ORGANIC MATTER IN WATERV . iOX ID IZED NITROGEN— NITRITES AND NITRATESVI . GASES IN WATER— WATER SEDIMENT— INTERPRETATION OF

RESULTS OF CHEMICAL iANALY SEsVII . THE BACTERIOLOGY OF WATER—E XAMPLES OF

'

WATERS FROMVARIOUS SOURCES

VIII . SEWAGE EFFLUENTSIX . SOILX .

- AIRXI . FOODSTUFFS:MILK— B UTTER— CHEESE— CEREALS— B READ

MEAT— ALCOHOLIC B EVERAGES— LIME AND LEMON J UICES— VINEGAR —M

-

USTA'

RD PEPPER SUGAR TEA COFFEECOCOA

XII . D IS INFECTANTS

APPEND IX

INDEX

L I ST OF I LLUSTRAT IONS

FIG. PAGE1 . Geo log ica l fault , etc.

2 . Curv e o f ground -w ater3 . D iagramm atic sch em e o f

o rgan ic po llut ion und er

go ing purification4 . Th resh

'

s apparatus5 22 . Objects found in w ater

sed im ents 69 , 70 , 7 1 , 72 ,

73 . 74 . 75 . 76. 7 7 . 78

23 . Adeney'

s appara tus 10324 . Barom eter and v ern ier

scales 12 1

25 . H empe l’

s gas burette andabso rp tion p ip ette

26 . Apparatus used in m ilkana lys i s

2 7 . Apparatus used in m ilkana lys is

28 . Apparatus used in butterana lysis

29 . Granules o f w heat starch30 . Granules of barley3 1 . Granules o f ry e

3 2 . Granules o f r ice33 . Granules Of o at34 . Granules Of m aize35 . Granules Of sago36 . Granules Of tap ioca3 7 . Granules o f pea

38 . Granules OI harico t b ean39 . Granules o f arrow roo t40 . Granules o f po tato4 1 . Vibrio tri tici42 . Bruchus p is i43 . Acarus farinae

44 . Pen icillium glaucum45 . Asperg illus glaucus46 . Muco r mucedo

47 . Pe rono spo ra48. Ustilago segetum

v iii

FIG.

49

50 .

. Po rt ion Of Fig . 50 more

Til letia caries (Uredo foetida)

Wheat stem Infected w ithpuccin ia

highly m agn ifiedTe leuto spo resZZEcid ium berberid is

Go n id iospo res and teleutospo re

E rgo t in rye

Sclero tium beari ng strom ata

Strom a con ta in i ng asco

carpsAscocarp con ta in ing asciAscus conta in ing ascosporesH ead o f cyst icercusTaen ia so l iumTrich ina sp ira l is

H ead OfD istom a hepaticumAscarus lum br ico ides

Oxyur is v erm icularis

Appara tus used in estima

tion Of alcoho l

Ce lls Of cut icle o f m ustardBlack pepp erCuticle o f tea - leafId iob lasts in section o f tea

leaf

Tea - lea fEld er- leaf

VVi llow leaf

Slo e leafCuticle o f tobacco leafCo ffee b erryGround co ffe e

,show ing cell s

o f testaLactea l v essels o f chico ry

79 Do tte d v esse ls Of ch icory

PRACTICAL SAN ITARY SC IENCE

CHAPTER I

GENERAL OBSERVATIONS UPON POTABLE WATERS IN

RELATION TO THEIR SOURCE, AND METHODS OF

EXAMINATION ADOPTED FOR SAFEGUARDING THEIR

PURITY

WATER is Often the v ehicle'

of infectious diseases , poisonous metallicsalts, and a large number of undesirable materials— animal , v ege

table , and . mineral . When we consider how drinking waters are

Obtained,and how liable

,

they are to contamination at all pointsfrom source to final distribution , it will be readily admitted that

every potable water should be the Obj ect of the most careful ,intelligent , and constant concern . The primary obj ect of a water

analysis for publicrhea lth purposes is to ascertain whether or not

it contains sewage , aS in the organic matter contributed by sewage

are found the organisms of infectious disease , such as B acillus

typhosus , Vibm'

o cholerw'

asiaticw, etc . All other information is of

very secondary import compared with this . The detection of or

ganic filth ,Whether of animal or vegetable origin , and of harmful

inorganic -matters ;"

when jn small‘

quantities , is often a work of no

little difficulty . In certain cases where a small amount of sewage

containing pathogenic micro- organisms finds its way into a water

supply , no chemical analysis , however delicate , can furnish evidenceof the pollution . SO al so in other cases the most exact bacterio

logical examination may Wholly fail to discover a dangerous water .The well - informed analyst will not pin his faith to one method of

examination to the partial Or total exclusion of others , but will

welcome all reliable methods that can assist in throwing light on his

Search .

PRA CTICA L SANITAR Y SCIENCE

At present four methods Of examinat ion are ut i lized— v iz

Physical , Chemical , B iological , Bacteriological— e ach of which has

its place and its limits .

The physical examination may detect pollut ion so gross thatfurther inquiry is unnecess ary .

The chemical analysis can render no informat ion concerningliability to contamination , and is useless in detecting small quanti

t ies of sewage . A systemat i c chemical analysis is ofvalue in demonstrating variations in character produced , for example , by the

lowering of the level of well waters , by change in rainfall , act ionon lead , iron , and zinc , in pipes , mains , cisterns , boilers , etc . Where

the estimation Of saline constituents must be determined for healthpurposes , manufacturing and engineering purposes , etc .

, the

chemical method alone is of value . Here it may be stated as a

general principle that waters most suitable for domest i c purposesare also most suitable for manufacturing and engineering purposes .

Acid waters corrode boilers , SO do waters containing markedquantit ies Of MgCl2 and CaCIZ, as these chlorides at high temperatures decompose , forming HCI, which at once attacks the iron .

CaSO4 , being insoluble , is deposited as a crust . CaCO3 and MgCO3together with salts . of Fe render water unsuitable for tanning,dyeing , paper-making , and other industries , owing to their greatinsolubility , whereby particles are left in the fabrics .

Neutral and alkal ine (NazCO3) waters are best suited for boilers .

Special chemical analyses are required in dealing with medicinal

waters .

By careful and systematic study Of the lower forms o f animal

and vegetable life,much information may be acquired as to the

source and mode of entry of surface waters into water- supplies .

Such biological examination has not had in this country the attention it deserves .

Where the question Of infective micro - organisms in water arises .

which to the sanitarian is of all questions the most important , thebacteriological examination only can afford positive evidence .

The examinat ion of the source of a water- supply is of the firstimport , and should never be omitted . Personal inspection Of thecatchment area , all streams arising therefrom , and all feeders Of

such streams, should be m ade in situ, and the relations Of these

GENERAL OB SERVA TIONS UPON POTAB LE WA TERS 3

to possible sources Of pollution carefully noted . When the gatheringground has been thoroughly investigated , attention Should be

turned to the storage reservoirs , and finally the efficiency of filtra

tion should be bacteriologically tested . Such examination presupposes an intimate knowledge of the entire area set apart for

collection , which Should be protected from all possibility of con

tamination from manured soil , house drainage , and storm waters .A good working knowledge Of the geology Of the district is essential ,and every student of water analysis should intimately cultivate

the solid and drift maps of the Ordnance Survey .

The following brief table gives an outline of themore importantstrata in this country, detailed descriptions Of which will be found

in any textbook of geology .

Post- tertiary d eposits

Alluvium , sands , gravels , boulder clay .

Tertiary deposits

Sands of the Eastern English counties .

Bagshot sands (upper, middle , and lower) .London clay .

Secondary”deposits

Chalk .

Greensands— upper and lower- e—With gault lying between .

Weal d clay .

Purbeck marble .

Kimmeridge clay .

Oolite .

Lias .

New red sandstones .

Primary deposits

Coal , ironstones .

Limestone .

Old red sandstones .Shales and slates .Crystalline rocks .

Shallow wells sunk in the post—tertiary sands and gravels arevery liable to pollution .

The Bagshot sands yield a fairly soft water.The London clay is an impervious stratum,

and the waters resting immediately on it are generallv hard .

PRACTICA L SANITAR Y SCIENCE

The chalk formations of England , which are extensive , yield

both hard and soft waters . The hardness is mostly temporary .

Fissures make it possible for pollut ion to readily get access to thesewaters .

The greensands , especially the lower, bear waters rich in calcium

and iron salts .

Oolites produce waters alm ost identical with those of the chalk .

The magnesium limestones (dolomite) and new red sandstones

give origin to much hardness , of which a large portion is permanent .

Slates and igneous rocks , being practically insoluble , yield waters

destitute of sal ine matters , and are consequently very soft .

e rm e a bl etr a t

‘

am .

Wa ter be a r inya tun .

mp e r m e abl es tr a tum

FIG . I .

The drainage area of a well depends upon the depth Of the well ,the porosity of the soil and subsoil , direction of flow of ground water ,and the daily depression produced by pumping . It may be considered as the base of a cone whose apex is the water - level in the well .Even with a good knowledge of the geology of the catchment

area and dist ricts through which the water passes , the analyst issubj ect to pit falls at al l points . Strata may contain caverns and

fissures which lodge pollution in the most unlikely posit ions .Geological faults account for unexpected positions of springs .

Where a water - bearing , permeable stratum i ntervenes between twoimpermeable strata , and a fault occurs , the imprisoned fluid may

become subj ect to such pressure that it escapes at the surface withtremendous force .

GENERAL OB SERVA TIONS UPON POTABLE WA TERS 5

It is to be noted that the curve of the ground water near the well

is steep , but rapidly shades Off into the horizontal . It is obviousthat with different types of soi l the form

'

Of this curve changes

as the surface water in the well is lowered . The drainage area

increases in direct proportion to the porosity .

This area Should be protected from all forms of organic pollution ,including cultivated soils, and it has been laid down as a minimum

requirement that it should have a radius of twenty times themaximum depression of the water through pumping i f the

depression in the well be 5 feet , the area should have a radius of100 feet , etc . Outside this cone '

it is considered that fil tration is

so slow that purification is complete . A wide margin , however,

O r a l/ri d ge A r e a .

Wa l l .

Ground wa te r l e v e l.

of Groun dwa te r

FIG. 2 .

should be allowed in the drainage area to meet the effects of in

creased rainfall,possible faults in the brickwork of the well , and

other factors, so that wells supplying drinking waters should be

removed widely from all sources of drainage, farmyard manure , etc .

A slight acquaintance with the situations of many rural wells in

this country must call forth unqualified condemnation . There isno doubt that many epi demics of typhoid fever have their origin

in the waters Of these wells . It is a matter Of little di fficulty todetermine whether or not l eakage from the immediate surroundings

takes place into a well, and an alkaline solution of fluorescin ,an

emulsion Of B aci llus prodigiosus, or a concentrated solution Of

NaCl, poured around its mouth and thoroughly washed into the soil ,will afford the necessary evidence within a

'

lim ited time .

Peat which lies for the most part on igneous rocks imparts to

PRACTI CA L SANITAR Y SCIENCE

water certain organic acids capable of dissolving metals . Wherever

possible such waters should be cut out Of a supply . If this cannotbe done the acids should be neutralized before the waters pass tothe consumer .Rivers and streams from which water- supplies are procured

should be scrupulously preserved from the entrance of pollution,

with a special view to the exclusion of infective bacteria . All river

water should be sedimented and filtered before use , and the efficiencyof filtrat ion Should be constantly tested by bacteriological examinat ion .

All forms of animal and vegetable life should be excluded from

service reservoirs , cisterns , mains , etc . I t is well known thatcertain low vegetable forms , especially when dead , give origin to

Offensive odours .

Water moves in a cycle . Evaporation produces clouds , which

return to the earth as rain . This rain , according to the nature Of

the soil , subsoil , and rocks , pursues various paths . If it fall onimpervious granite it runs Off in large quantity ; a part may be

evaporated , and this will occur to the greatest degree during dry ,

hot, and windy weather . If it fall on sandy soil a large proport ionpercolates , and the more porous and deep the sand ,

the more

rapidly and deeply the water sinks into the earth . When it meets

with an impermeable stratum its further course is directed by the

slope and contour of this stratum . Should the latter take the form

of a basin the water will accumulate until it overflows the lip of thebasin , forming a spring at a point where the stratum outcrops .

Again , if the stratum form an inclined plane , as on the sides Of ariver valley , the water will flow along the plane to its outlet at the

lowest point . Such pure waters may be intercepted before reaching polluted rivers by sinking wells at the bases of the hills forming

the sides of the river valleys . The upper surface of this mass Of

moving ground water is indicated bv the lev el Of the water in superficial wells . This surface is not necessarily horizontal . It is in

constant motion , travelling towards the outflow, and the rate Of

movement is governed by the porosity of the soil , mpe , nature ofoutlet , etc . An intimate knowledge of the entire history of a waterwill often be necessary to an intelligent comprehension of certain

analyt ical data .

CHAPTER I I

THE PHYSICAL EXAMINATION OF WATER

THE physical examination comprises a determination of the tur

bidity, colour, Odour, and- taste“Turbidity.

—Pure waters are free from Visible particles insuspension:the slightest degree of Opacity should render a watersuspicious . On the other hand , the most transparent and brilliantwaters may contain the most pronounced pollution . Turbidity

may be produced by access Of the contents of cesspools , drains ,manure heaps , and surface refuse of all types , especially after rains ,when it forms often the Worst kind of pollution . It may be pro

duced by particles of clay, iron , chalk, etc., when a chemical and

microscopical examination may be necessary to disclose the nature

of the matter in suspension . Waters containing iron very Often

deepen in opacity during the first day or two after collection , owing

to the formation of persalts of that metal , which are highly insoluble .

Such opacity imm ediately disappears on the addition of a smallquantity of diluteHc1.

Estimati on of Turbidi ty.—Place the Winchester on a white

porcelain tile in a good north light , and examine it carefully

wi th the naked eye . Much information regarding opacity, sedi

ment , etc . , m ay thus be gained by a practised eye .

The sample may be described as brilliant (aeration good) , clear,slightly turbid or Opalescent , turbid, markedly turbid . TO estimate

the quantity of matterin suspension , filter 100 cc . through a hard

filter and evaporate in a platinum dish to dryness . The differencebetween the weight oftHe

‘

residue dried at 100° C. and that of 100of the unfiltered sample similarly treated will represent the desired

result . Or, where a centrifugal machine is available , by means ofsmall tubes the sediment may be read Off quantitatively on a gradu

8 PRA CTICA L SANITARY SCIENCE

ated scale . The amount of light permitted to pass through a columnof Opalescent water mounted in a glass cylinder can be matchedby the illumination Of a polarized light ray passing through asecond similar glass cylinder containing no water ; the degree of

rotat ion of the Nicol Of the eyepiece expresses the degree Of

turbidity .

Colour .—Uncontaminated rain water presents a pale blue t int

in the ‘ two - foot tube . Yellow tints point to organic matter ,brownish - red suggest a peaty origin , and reddish - yellow indicateiron . Any appreciable shade of yellow or brown wi ll excite suspicion

"

, and lead to a careful search for the cause’

. Colour tables

have been formulated for the use of water analysts , but do notseriously assist a trained eye .

Clean thoroughly and fil l the two - foot tube ; place it on the tile ;look down through the column , noting the tint of colour , which m av

range from a pale sky- blue to a yellow or brown .

As to colour , for all ordinary purposes the naked - eye inspection

is sufficient , but if for any reason great accuracy is required a tintometer may be used . Two hollow glass wedges containing respec

tiv ely di lute solutions of CuSO4 , and a mixture of ferri c and cobaltct rideS slightly acidified , are made to slide over each other infront of an empty tube , so that any desired combinat ion of blueand brown tints can be Obtained . Alongside is placed a similar

tube fil led with the sample , and the wedges are arranged so that on

looking down upon a white surface the colours exactly match . The

prisms are graduated in mill imetres , and the results are expressed

in terms of mill imetres of blue and brown .

Water may be variously coloured by algae and other vegetableOrganisms . Crenothrix polyspora (rich in iron) colours it red o r

reddish-brown , and decomposing accumul ations of the dead or

ganism may produce serious nuisance . Green and blue algae produce

their respective tints , and peat , according to its concentrat ion , all

shades of brown .

Odour.—Drinking water should be free from all Odour . Dis

solved gases may be liberated by'

slightly‘

warm ing the water, sayto a temperature of 37

°C . In the case of peaty waters it has been

found at times that even after the most careful fil tration a slightodo

‘

ur still attaches to the water . For many reasons peaty wate rs

THE PHYSICA L EXAMINA TION OF WA TER 9

do not furnish good supplies , and where other sources are available

should be passed over .

River waters usually have a faint smell , due to a variety of causes ,most often , perhaps, to vegetable organisms , some of which

the well - known sewage fungus— are associated with the production

of H28 .

The dead and decomposing remains of plants and animals furnish

a variety of odours , not only in river waters , but in cisterns , reser

voirs , and mains . Of late years attention has been called to distinctspecies of lowly vegetable forms which produce disagreeable odoursin water .

It is customary to obtain the'

sample of water for physical examination from the vessel containing that for the chemical examina

tion , and something may now be said respecting the mode of collecting such samples . The SO- called Winchester quart bottle has long

been used for this purpose,and when made of colourless glass

answers the purpose admirably . The bottle should be thoroughly

cleansed by rinsing with dilute HCl , and afterwards removing thelast trace of acid with distilled water . Where it has to be sent byrail , etc . , it is packed in a t ightly - fitting wicker case or woodenbox fitted with padlock . B eforefilling , the bottle should be rinsedwith a portion of the Sample . A little air space should be left underthe stopper to avoid cracking of the neck through rise of temperature . Procedure in collection will vary according to the obj ect ofthe examination . I f it is desired to ascertain whether , for example,lead is dissolved by a water in the house - pipes , it will be necessary

to collect the first runnings from the taps in the morning . When

a bacteriological examination is requi red , a special method must bepursued , which will be described later . Where the sample is to betaken from a river, cistern , etc . , the bottle , prepared as above , i s

usually immersed some little distance below the surface , where the

stopper i s removed and the bottle filled . A small portion is pouredout in order to procure the air Space mentioned , and the stopper

inserted . Various forms of apparatus have been devised for collecting samples under different conditions , but the circumstances willin all cases suggest the mode of procedure , if i t be kept in mindthat a fair sample of the water as it is usually found is the obj ectdesired .

I o PRA CTICA L SANITAR Y SCIENCE

A correct record of the sampling process , etc ., should be made on

the spot , and attached as a label1 . Date , time , and place of taking sample .

2 . Depth below surface , state of water - level— high , low , o r

average .

3 . Part iculars of rainfall and of geological strata of district .

4 . Depth of water- level below ground- level .

5 . Descript ion of surroundings , possible sources of pollution , such

as sewers , cesspits , cemeteries , etc .

In many cases it is well for the analyst to supply his own collecting - bottle , with instructions for taking the sample and filling up the

label . The sender should be made to understand that the specimen

must be of the same nature exactly as that actually consumed , and

that it is desired to ascertain the maximum degree of pollution thatmay at any time obtain . All such part iculars , as also the resultso f the analysis , should be transcribed into a book and preserved forfuture reference .

Estimati on of Odour . Place 250 c . c . in a stoppered flask,and heat to 37

°C . in an air—bath . Remove the stopper and

smell . I t is generally sufficient to shake the sample well in the cold .

rapidly remove the stopper , and smell‘

. The variety of odours isinfinite . Many odours are produced by organisms , either as products

o f their life—history or of their death and putrefaction . B eggiatoa,Chara , and certain species of Crenothrix produce an offensive odour

of H28 . I t is believed that B eggiatoa during its life - cycle reduces

sulphates , and produces under favourable circumstances largequantit i es of H

25 . Crenothrix, moreover, Often produces abundance

of colour , varying from brown to red . Tabellaria , Meridion , and

certain diatoms , as also the protozoon Cryptom onas , furnish a dist inctly aromat ic odour . A fishy odour is produced by Volvox and

the protozoa G.cnodinium , Bursaria , and Uroglena . A grassy

odour accompanies R ivularia, Anabaena , and Caelosphaerium .

Taste .— Pure rain water well aerated has a fairly distinctive

taste , more easily appreciated than described . So also have peaty

waters , sea water , and chalybeate waters . The taste of a particular

sample may be , however , everything to be desired , whilst the wate ris the foulest of the foul . Taste , however, is of little service to theanalyst , and not always to be recommended . Iron is about the

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CHAPTER I I I

THE CHEMICAL EXAMINATION OFWATER

IT will be well for the student from the first to fit up his own appa

ratus , and make his own standard solutions . He must learn touse properly the chemical balance , and a special demonstration is

devoted to the mechanism , methods of adjusting and using thisal l- important instrument . B efore commencing to weigh , he should

see that the balance is accurately levelled , and that the index moves

without effort over the whole field of the graduated scale , and comes

to rest at zero . All weights , basins, etc . , should be transferred toand from the scale- pans only when these are supported . It is

customary to use three rows of weights , grammes (brass) , decigrammes and centigrammes (platinum) , and milligrammes (platinum) . A rider of platinum applied to the beam also reads milli

grammes . The right - hand pan should be used only for weights ,and these should be placed methodically in three rows in front of theoperator . By this means the total reading is most easily obtained

and checked .

Immediately on fin ishing a weighing all weights Should be transferred to the box , with the forceps used for the purpose , and the boxand balance carefully closed .

The standard solutions in use in water analysis are of two types:I . Normal , decinormal , centinormal , etc .

2 . St andards of such strength that a litre contains the equivalent

of a gramme , or submultiple of a gramme , of the substance to be

estimated .

A standard solution is said to be normal when one litre contains

the equivalent weight in grammes of an element , acid, alkali , or

salt .

The molecular weight of HCl is therefore grammes

HCl per litre= normal HCl, written N .HCl .

1 2

THE CHEMICA L EXAMINA TION OF WA TER 13

In like manner N .NaOH= 4o grammes per litre .

Since the term equivalent signifies the weight in grammes of the

substance under consideration , which is chemically equivalent to

1 gramme of H , normal HzSO4 49 grammes per litre .

A decinormal solution (TN

U) is one - tenth the strength of a normal—thus T

N

U NaOH= 4 grammes per litre— and a seminormal (g) andcentinormal (r ife ) are respectively one- half and one -hundredth the

strength of the normal— v iz , 20 grammes and 04 gramme per litre

respectively .

In tribasic acids one- third of the molecular weight in grammesper litre constitutes a normal solution , and so on for acids of higher

basicity .

The terms normal , decinormal,’ etc . , are used sometimes with a

different mea-nlng . Permanganate of potassium , as we shall see

presently, in'

acid solution i s reduced by many substances, accord

ing to the equation K2Mn208 KzO zMnO Os , in which

2 gramme molecules of KMnO4 correspond to 5 gramme molecules

of oxygen or to I O gramme molecules of hydrogen . Accordingly,in order to put permanganate of potassium on a hydrogen basis , a

3 163

I O

per -litre . In the same way K2Cr207 , which in acid solution parts

294'

5

(c r207

6

grammes per litre .

The second type o f standard solution used is constructed so that

a minimum amount of calculation suffices in estimating resul ts .

Since it is customary to represent the various items of the analysis“

as parts by weight per of the water, and since 1 c . c . of water

weighs 1 gramme milligrammes) , 100 c . c . of water will weighmilligrammes .

It is therefore convenient , when possible , to work on 100 c.c. of

the water sample throughout the various estimations,and to use a

standard solution that will give readings directly in the aboveterms .

Suppose we wish to estimate the quantity'

of Cl in -

a water , weuse a solution of AgNOan of such

“strength that 1 is equivalent

normal solution is made to contain 3 1°63 grammes

with O3 , requires for a normal solution

I 4 PRA CTICA L SANI TAR Y SCIENCE

to 1 milligramme Cl . To m ake this solution we refer to the m olec

ular weight of AgNO3 , and the atomic weight of Cl . AgNOa-l

\l

aCl AgCl NaNO3 .

170 grammes AgNO3 precipitat e grammes Cl .dividing by 35 -

35 , we find that 48 grammes AgNO3 precipitate1 gramme C] .

If, then ,we dissolve grammes AgNO3 in 1 litre of water we

obtain a solution 1 c .c . of which precipitates 1 milligramme of Cl ,and working with 100 c .c . of water , the number of c .c . of thesilver nitrate solution used indicates the number of milligrammes

of C1 in milligrammes of the water , which is parts per

Again ,in estimating NH

3a standard solution of NH4Cl is pre

pared and used in the same way .

One molecule of NH Cl contains 1 molecule of NH53 35 grammes contain 17 grammes

and 1 gramme

Therefore a litre containing 3 14 grammes NH4C1 will contain

1 gramme NH3 ,and consequent ly 1 c .c . contains 1 milligramme .

It is found convenient to dilute this 100 times , so that 1 c .c .=

milligramme NH3

.

Standard solutions Should be stored in bottles in such manner

that both internal and external evaporation are impossible . In

the first case , where the bottle is not quite full , pure water willevaporate and condense on the upper portions of the vessel ; in the

second , evaporation will take place into the atmosphere . The lossof water will naturally depend on the substance dissolved, the temperature , the age of the solution , and the frequency with whi ch i t

is used . A rough estimate may often be made of the probableamount of change in strength by noting the date of preparation ,

which should always be found on the label . Some standards undergo

chemical change by the action of light , and Should therefore be keptin the dark .

In reading a burette,arrange it so that the lower convex line of

the meniscus is in the same horizontal plane with the eye ; the

THE CHEMICA L EXAMINA TION OF'

WATER I 5

division of the scale cut by the lowest point of this convex line isthe reading .

_

In m easuring small quantities of liquids much time may be saved

by using a few plain I O c .c . pipettes graduated to tenths of a c .c . , and

for quantities under a c .c . a 1 c .c . pipette graduated to hundredths .

These can.

be easily and rapidly cleaned,and as easily and rapidly

manipulated,and may often take the place of burettes . In

weighing platinum and porcelain basins , crucibles , etc ., it is very

necessary to see that they are quite dry . To insure this , especially

after heating , they Should be placed for ten m inutes in a desiccator

immediately before going to the balance . It is also necessarv to

be certain that all such vessels are thoroughly clean . Accurate

notes of all operations , measurements , weights , etc .,should be made

in the bench notebook,and considered as much a part of the work

as the Operations themselves . Without this notebook it is impos

sible to get on with analytical chemistry . Where possibl e it is well

to writ e down the chemical equations representing decompositions .

When in doubt in this matter refer to a work on chemistry . All

colour matches are best made in glass cylinders standing on a white

ground, as the Operator faces a north light .

The Reaction of Water.—This is an important item , and

Should form the first step in the routine chemical examination . Inaddition to the use of red and blue litmus -papers , it i s often well touse a more delicate indicator, such as phenolphthalein ,

and to esti

mate the amount Of acidity (when acid) in 100 c .c . by t itrating withNaOH , o r of alkalinity (when alkaline) with —1

N—0 Hz

SO4 . An acid

water dissolves lead, iron , and zinc ; it also fixes ammonia , and so

prevents its being distilled off. Some hold that neutral waters and

those possessing very slight temporary hardness are capable of

dissolving lead . It should be remembered,however

,that sodium

carbonate when present prevents this action . Houston has corre

lated the acidity and plumbo - solvency of a large number of moorland waters .

He causes the sample to percolate upwards through a columnof Specially prepared lead shot at a uniform rate . He then

collects successive 50 and estimates the amount of lead ineach .

The following figures are taken from a report to the L .G.B .

16 PRA CTICA L SANITAR Y SCIENCE

Acro i r v . PLUMBO -SO I.VENCV.

N umbe r o fc.c. Mgms . o f Pb in

N; NagCO3 requ ired to neutra l ize 100 c.c. of the Wa te r afte r100 c.c. o f the Wate r. Fil tration thro ug h Lead Shot.

0 -28

0-250 -

40 -66

0 -

92

2 -66

2 -8

8-6

Some waters not acid , and failing to dissolve lead ,exert an

erosive action , forming an insoluble film of oxyhydrate upon

the lead, which after a time may become detached ,and produce a

degree of opacity .

Chlorides in Water . Free Cl rarely occurs in water - supplies .

Certain manufacturing effluents may on occasion contain small

quantiti es of free CI, but the quantity is SO small and the occurrence

so rare that this form of Cl may be practically ignored . The great

bulk of Cl in drinking water is found as NaCl . All soils and sub

soils contain this salt in large amounts . The water-bearing strata

are rich in chlorides , especially NaCl, and consequently rain water

(which itself may contain as much as 0 -

5 part per NaCl) ,as it percolates from the surface to the impermeable stratum on

which it rests , dissolves these in considerable quantities . CaCl2

and MgCl2 are found in certain strata— chalk and limestone— in

much smaller quantit ies,but MgCl2 abounds in sea water, and inlarge quantity is distinctive of it . Wells , reservoirs , etc . , to which

sea water can obtain access will yield waters rich in MgClz. Sources

of water subj ect to much evaporat ion,especially if situated near

the sea,exhibit large quantities of chlorides . The total C1 in sea

water approaches parts per and if this figure be kept

in memory it will explain the large estimations often found someconsiderable distance from the littoral . During the passage ofwaterthrough the soil , subsoil, and strata , C1is not

’

likely to be diminished

as are the organic matter and bacteria .

When we have accounted for all the Cl contributed by rain water,

THE CHEMICA L EXAMINA TION OF WA TER 1 7

sea water , soil , subsoil , and strata, and trade effluents from chemical

works , paper factories, etc . , there may remain a surplus furnishedby organic pollution of animal origin . This surplus is of someimport to the analyst , as indicating sewage ; butb efore it is returned

as Such all the possible sources of origin just mentioned must be

rigidly excluded . Vegetable organic matter does not yield this

surplus Cl . Attempts have been made in US A . to estimate andpermanently record the Cl due to the natural causes named, so that

sewage pollution may be readily detected . Maps have been con

structed and points furnishing equal quantit ies of Cl j oined by lines

named isochlors .

’ In districts remote from the sea, and centres

of population and land cult ivation such maps may be more or less

reliable , but in this country they Would be useless . Whilst it is

true that animal pollution contains much Cl (urine about I per

cent . chlorides) , and that soils , strata, etc . , in certain districts yield

fairly constant quantiti es, still there are variations in many localiti es

in these natural sources , and it is only where large quantiti es of sew

age,have gained access to waters that we can rely on the surplus

Cl as evidence of this accession . In the case of small amounts of

sewage this surplus Cl figure is of little if any value . But in awater

analysis the Inost important information li es very often not so much

in the exact amount of a particular constituent as in the fact that its

presence points to past pollution,and consequently to the possibility

and even probability of a recurrence of such pollution . I n this

light Cl and nitrates play an important rOle . These afford unm is

takable evidence of '

prev ious contamination ; they are the distinct

and unchangeable indications of previous pollution , but as to

whether recent or remote they indicate nothing . Hence the mecessity for further and different forms of examination . As to the

amounts of chlorides that should condemn waters , it is difficult toSpeak, S ince there is such infinite vari ety in the quantities containedin different soils and strata “

. MgCl2 and CaCl2 render waters hard ,

so that more than 4 or“

5 parts of either or both of these perwill cause a large destruction of soap

, and these figures w i ll in mostcases form the lim it for domestic waters . NaCl may go up to

'

perhaps 50 parts per above this it imparts a taste,and the

water consequently will not be fit for drinking .

1 8 PRA CTICA L SANI TAR Y SCIENCE

Estimation of Cl.

APPARATUS AND REAGENTS REQUIRED .

Awhite porcelain basin capable of holding 250 c .c .

A glass stirring - rod .

A burette charged with standard solution of AgNO3 , of which1 c .c . i s equivalent to 1 milligramme Cl (4 8 grammes AgNO3 to alitre of water) .A 5 per cent . solution ofK2CrO4 .

Place 100 c .c . of the water in the porcelain dish .

Add 1 c .c . of the K2CrO4 solution , and stir .

Run in from the burett e drop by dI Op the silver nitrate solutionuntil the pale yellow colour remains perm anently orange .

Take the reading .

The rationale of the process is as follows:AgNO3 , when added to a solution of chlorides , forms AgCl, a

white curdy precipitate insoluble in HNO3 , soluble in NH4HO .

Without a special indicator it would be impossible to determinewhen the whole of this white precipitate had been formed— when the

whole of the Cl had been deposited .

K2CrO4 is also acted on by AgNOa, and An rO

,1formed , which is

red . But so long as any chloride remains ununited with Ag , the

S ilver chromate is decomposed and AgCl formed ; hence the dis

appearance Of the red colour on stirring . Immediately the wholeof the C1 is precipitated as AgCl the red silver chromate remains .

The reactions are represented by the equations

AgNO3 NaCl AgCl NaNO3 .

2'

AgN03 K2CrO4 An rO

42KN0

3.

2NaCl An rO4 2AgCl Na2CrO4 .

It is obvious that the K2CrO4 should be free from C1. Acidity inthe water will dissolve Ag2CrO4 ; hence if a water is even slightly acid

it must be neutralized . Freshly precipitated CaCO3 is the best alkalito use , and it Should be used only to the point Of neutralization .

If too little KzCrO4 is used the Cl reading will be too high ,

and if

too much be used it is difficult to determine the end ; 1 c .c . , accord

ingly. is found a suitable quantity when the solution is of the above


of the water may be concentrated by evaporation to 100 c .c .

Alkaline silicates , nitrates , and phosphates slightly affect the Clest imation , but not to such a degree as to require correction .

Chlorine is sometim es returned in t erms of sodium chloride

This figure is found by multiplying the Cl return bygi—g—g. WhereCaClz, or MgClz, or both ,

enter into the problem corrections haveto be made in accordance w ith the respective molecular weightsand the quantities of each present .

In chalk and red sandstone waters 3 parts of Cl per mayoccasion no suspicions of sewage , and 4 or 5 parts may be passed ,unless organic pollution is indicated by other items of the analysis .Pure surface waters seldom contain more than 1 part per

whilst deep greensand waters m ay give rise to 15 to 20 parts perand still be absolutely pure .

The following are a few examples of the Cl figures for different

waters

A w ell in St. PancrasLamb eth w ater- supply

Southwark water- supplyA w e ll in D ev onsh ire

Tham es w ater at Waterlo o BridgeDeep w e ll near H indhead

Samp le of rain water taken from ra in gauge H erts

Hardness.

The hardness (soap -precipitat ing power) of a water exerts littleinfluence on health

,but from an economic point of Vi ew is of some

im portance .

A soap is a chemical salt formed by the union of an inorganic

base with one or more fatty acids .

Sodium and potassium soaps are soluble in water, and when

shaken with it form a dense froth or lather . Calcium and magnesium soaps are insoluble in water , and fail to form a lather . Hence ,if a solut ion of a soluble soap be added to water containing calciumor magnesium salts , these last will be completely precipitated inthe form of insoluble calcium or magnesium soaps before a lather

i s produced . Accordingly, by using a standard soap solution , an


approximate estimate of the quantity of such soap -precipitating

bodies in a water can be made . The total quantity of such bodies ,as measured by the standard soap solution, constitutes the totalhardness . Other bodies than calcium and magnesium salts areoccasionally present in water, which act in a Similar manner on soap .

If much sodium chloride be present,it will precipitate soap from its

solution in an unaltered state .

CaCO3 and MgCO3 , especially the first , have by far the greatest

share in rendering waters hard . These salts are formed in solution

in the soil as bicarbonates [Ca (HCO3 )2 and Mg (HCO3 )2] by CO2dissolved in rain water . On boiling such waters , CO2 escapes , andinsoluble carbonates separate out as a precipitate

Ca (HCO3 )2 ->CaCO3 CO2Hz

'

O.

The addition of slaked lime to_water containing the bicarbonates

_of the alkaline earths results in the precipitation of the lime added

and the bicarbonates thus:

Ca (HCO3 )2 Ca (OH)2 2CaCO3 2H O . (Clark’s process .)

It now the boiled water be filtered,made up to its original volume

with distilled water, and again titrated with standard soap solution ,the permanent hardness is obtained .

The differen ce between the total and the permanent hardness isthe t emporary h ardness .

The soap test has been made to measure the quantity of CaCO3and other salts which produce hardness , -but this is not accurate

quantitative analysis . It should be crearly understood that the

chemical action is multiple and indefinite, and altogether different

from that which usually takes place, when in quantitative analysiswe titrate one definite compound against another . All that canbe claimed for the soap process is that it indicates the amount ofsoap—destroying bodies present in a given water, but fails to forma measure for any in particular .The following compounds produce hardness:CaCO

3 ,MgCO3 , CO2 in solution , CaSO4 , M

'

gSO4 , PezO3 , and otherPeroxides , zinc salts , SiOz, Alz (OH)6, chlorides , nitrates , phosphates ,and free mineral and organic acids .

The temporary hardness , which is got rid of by boiling,is for

2 2 PRA CTICA L SANITAR Y SCIENCE

the most part produced by CaCO3 and l\lgCO3 , held in solution byCO2 . After these come small quantities of CaSO4 and MgSO4 ,which are also thrown out immediately CO

2is driven off, but the

great bulk of theseLsulphates remains in solution . Lastly , in afew cases minute quant it i es of oxides of Fe , silica , and alumina

are deposited . Phosphate of Ca , i f present in appreciable quantity ,may, under certain condit ions , be deposited in very small amounts .

On cooling some of the precipitated MgCO3 , and to a less degreeCaCO3 , CaSO4 , and will redissolve and go to form per

manent hardness .

MgCO3 destroys nearly 50 per cent . more soap than CaCOa, but

is found in potable waters in very much less quantity .

Estimation of Hardness.—Prepare a standard solution of

calcium chloride in the following manner:Weigh accurately 0 -2

gramme pure calcit e (CaCO3 ) , and dissolve it in dilute HCl , takingcare to keep the vessel covered so as to av o id loss by spirt ing . Evap

orate this solution to dryness on the water - bath . Add water , and

again evaporate to dryness,and repeat these processes in order to

remove all free hydrochloric acid‘

. Now dissolve the residue ofneutral

CaCl2 in water and make up to a litre . One c .o .= the equivalent

of 0-2 milligramme CaCO3

. In other words , this solution possesses

hardness : 20 parts perPrepare a standard soap solution by dissolving about 13 grammes

of Castile soap in a litre of equal parts methylated spirit and water .Stand in a cool place for some hours , and filter .

The titration and dilution of this soap solution is carried out asfollows:Make up 50 c .c . of the calcium chloride solution to 100 c .c . with

dist illed water (10 parts hardness per and place in a

stoppered bottle of 250 c .c . capacity . Run in from a burette , 1 c .c .

at a t ime , the soap solution . Close the bottle , and Shake vigorouslyfor a short period until a lather remains on the surface as an un

broken layer for five minutes . Towards the end of this operationthe amount of soap solution added should be lessened , and finally

should not exceed c .c . As the end is reached ,the sound and shock

produced by shaking becomes much more gentle .

The student should carefully prepare a number of similar lathersby shaking 100 c .c . distilled water in a similar bottle , and note

exactly the amount of soap solution required . This quantity

THE CHEMICA L EXAMINA TION OF WA TER‘

2 3

will be found to be about 1 c .c . of the finished standard soapsolution .

In the present case the quantity of soap solution used should be1 1 c .c . (10 c .c . to prec1pitate the equivalent of 10 milligrammes of

CaCO‘

g , and 1 c .c . to produce the lather) . Suppose , however, that9 c .c . soap solution be found sufficient to produce the characteristiclather, it is evident that the solution must be diluted with aqueousSpirit in the proportion of 9 to 1 1 . Dilute, therefore , 900 or

900 x 1 1

9

keep the remainder for fortifying the standard, as in time it losesstrength , especially when, on keeping, it becomes turbid . Labelthe solution Standard Soap 1 c .c .

= I milligramme CaCO3

.

Should the soap solution prove too weak,it must have additional

soap added and be put through the same process of standardizationuntil found correct .A standard soap solution may be prepared In another way:

Dissolve 80 grammes chemically pure oleic acid in alcohol, add afew drops phenolphthalein and- a strong solution of KOH in alcohol ,until the oleic acid is neutralized and saponification therefore com

plete (the liquid retains the faintest purple colour) then titrate withthe calcium chloride solut ion

,and dilute to standard strength .

The following is an example of the determination of the hardness

of a sample of a London (New R iver) water:Take 100 c .c . of the water in a zoo - c .c . stoppered bottle . Fill

a 50- c.c. burette mounted on a stand with standard soap solution

(1 c .c . 1 milligramme CaCO3 ) . Run in the soap solution 1

at a time , shaking vigorously after each addition , until a permanentlather remains unbroken for

rfiv e minutes when the bottle is laid on

its side . As the end of the reaction approaches , the hard metall ic

sound at first heard on Shaking gives place to a dull thud , the froth

which previously disappeared almost instantaneously remains, and

adheres in specks to the Sides of the bottle .

Twenty- one c.c.

‘

of standard soap solution were required in thi s

case to complete the titration . Subtracting 1 c .c .. used in producing

the lather, we find that 20 were precipitated by the 100 c .c . of

water .

thereabouts, of the original litre to the volume c .c . , and

But e ach c .c . 1 milligramme CaCOs ;20 c .c . 20 milligrammes CaCO


and 100 c .c . of this water contains 20 milligramm es of soap-

precipi

tating substances,or a total hardness equal to 20 parts per

In waters containing magnesium salts the lather is slowly

produced,and of a dirty ,

granular appearance , v ery unlike the

light frothy condition seen in hard waters destitute ofMg salts .

To obtain the perm anent hardness in the above example , place

100 c .c . in a small beaker on a porcelain ring over a Bunsen flame ,and boil for fifteen minutes

,or t ill one - third of the volume has

evaporated . Filter into a clean 100- c .c . flask , and make up to the

mark with distilled water . Transfer to the stoppered bottle and

determ ine the hardness as above:this is perman ent hardness .

’

13-

5 c .c . of the soap solut ion were required to lather the 100 c .c .

of water prepared as described .

13-

5 c .c .— 1 c .c . 12 -

5 c .c . ,

or 12 -

5 parts permanent hardness perThe t emporary hafdness difference between total and

permanent hardness .

20— 12 -

5= 7-

5 parts temporary hardness per

Hard waters, whilst palatable , cause waste of soaps , and fail

somewhat in cooking vegetables , meats , etc . , and in making infu

sions of t ea and coffee . They are unsuitable for boilers , in that a

deposit form s on the interiors which by reason of its low conductivityof heat wastes fuel

,and from its divergent coeffici ent of expansion

may lead to explosions .

This deposit or crust will consist of bodies representing both

temporary and permanent hardness . Carbonates of Ca and Mgwill fall out first

,and be followed by their sulphates , together with

salts of iron,sil ica

,and alumina .

In this country the hardest waters arise from the chalk ,dolomite ,

and new red sandstone strata , carbonates of Ca and Mg forming by

far the largest proportions of soap - destroying compounds .

Where the hardness exceeds 20 part s per it is well in

performing the estimation to dilut e the sample with an equal bulkof distilled water . The total hardness of .a potable water should .

not exceed 25 to 30 parts per Waters whose hardness

falls below 10 parts are considered soft , whilst those containing20 to 30 parts are hard , and upwards of 30 parts very hard .

THE CHEMICAL EXAMINA TION OF WA TER 2 5

Clark’s scale of degrees represents hardness as g rains per gallon

(parts perIt is universally agreed that a good water Should contain less

than 10 parts per of permanent hardness , and of this littleShould be due to magnesium salts .

Temporary hardness can be easily got rid of not so permanent .

In Clark’s process,as noted above, slaked lime is used for soften ing

—in other words,for combining with the CO3 ]in solution , thereby

causing insoluble carbonates to separate out which were prev iouslv

held in solution by the CO3 . Care should be taken that no excess of

lime is added .

CaCO3 , HzO, CO2 Ca (OH)2 2CaCO3 2H3O .

Softening of permanent hardness may be effected by the use of

NazCO3°

CaSO4Na

3CO

3Na3SO4 CaCO3 .

Clark’s method does not yi eld accurate results if a large quantity

ofMg salts is present . These salts do not materially affect the pro

cess now t o be described .

Estimation of Hardness by Standard Acid .—Determine

first the temporary hardness by titrating the calcium and magnesium

salts which form it with 333 HzSO

4 ,using methyl orange (the sodium

salt of a colour acid which is not interfered with by CO3 ) as indicator .

Add to 3 litre of the water , or less if it be very hard , 4 or 5 dropsofmethyl orange solution

,and run in

TN

o H3SO4 from a burette until

the colour changes pink . Calculate the weight of CaCO3from the

number of c .c . of acid used and convert this into parts perExample .

— 500 c .c . water required 9 c .c . decinormal sulphuri cacid .

1 c .c .

l

N—OHzSO4= I c .c. T

Nrr CaCO3: 0-005 gramme CaCO3 ;

500 c .c . water: 0-005 x 9 gramm es‘

CaCO3 ;100 water: 0-001 x 9

o 009

9 milligrammes CaCO3 .

Hence the temporary hardness in terms of CaCO 9 partsper 100,000 .

Permanent Hardness.—To 250 c . .c water add excess Na

3CO3 ,

say, 50 c .c and boil for half an hour . Should Mg salts be present ,

26 PRA CTICAL SANITAR Y SCIENCE

evaporate to dryness and extract the residue with water . Filter .

Wash the precipitate with boiled distilled water . Cool , and make

up the‘

fi ltrate to 250 c .c . T itrat e,say

, one -fifth of this with{5 H3

SO4 , using methyl orange as indicator . Calculate from the

number of c .c . acid used the weight of NazCO3 engaged in precipi

tating the salts forming hardness,and from this the permanent

hardn ess in t erms of CaCO3 ,in parts per

Example .— 50 c .0. taken from the 250 c .c . cold filtrat e required

8-8 c .c .

N—zH 80

4for neutralization .

250 c .c . require 88 >< 5 = fUHHSO50 44=

N3 Na2CO3 used

6 c .c .i t, CaCO3

0 005 x 6 grammes CaCO3 in 250 c .0 . water0 030

100 c .c .

2‘

s0 '012

or 12 parts perTemporary hardness , 9.

Perm anent hardness , 12 .

Total hardness, 21 .

Water containing Na3CO3 is alkaline in reaction and contains no

permanent hardness . Since boiling fails to interfere with Na3CO3 ,this salt can be est imated in the filtrate from the carbonates of Ca

and Mg precipitated by boiling in the above process , for the determinat ion of permanent hardness . The number of c .c .

I‘% H3

504

used x 0-0053 = weight of Na3CO3 .

Rain water is the softest of all natural waters , and hardness in

creases in the following order:Upland surface water , river water ,spring water , deep -well water

, Shallow—well water .

Calcium salts react quickly in the double decomposition with

soaps ; magnesium salts react more slowly . Hence, where magnesium salts are present in quant ity

,a more prolonged shaking is

necessary in producing the characteristic lather .

Where it is desirable to estimate the quantity of Mg present in a

sample , the ordinary methods of quantitative analysis must be

employed .

In using the soap test , hard waters should be diluted so that notmore than 16 c .c . of the standard soap solution is required to complete

the reaction .


shaking . The method adopted,however , should be stated on the

report .

Measure out 100 c .c . of the water , and place in a clean platinumbasin on a water -bath

, 25 c .c . at a t ime , as evaporation proceeds .

When dry, transfer the basin , after carefully wiping the outside ,to an air-bath at 37

°C . for half an hour . Rem ove to a desiccator

for ten minutes , and weigh . By drying at this low temperatureno water of crystallization is lost , and no decomposition takes place .

Further drying should be effected , if necessary, until a constant

weight is obtained . This weight , l ess that of the dish ,represents

the total solids .

With platinum - tipped tongs hold the dish over a Bunsen flame

until thorough incineration is effected . After cooling in the desic

cator, weigh again to obtain the non - volatile solids . The difference

between this last and the previous weight represents the volatile

solids . The degree of charring (organic matter) which occurs duringincineration should be noted ; also the smell— odour of burntsugar indicates vegetable matter , burnt horn animal substance .

Ca.— VVhere it is deemed necessary to estim ate the quantity of Ca

salts , Mg salts , or both , 500 c .c . of the sample should be evaporated

down to 200 c .c . , and the Ca removed by precipitation with

(NH4)HO, NH4Cl, and (NH4) 3C3O4 . The precipitate of CaC3O4 ,

when thoroughly washed,dried, ignited , and weighed, represents

the Ca as CaCO3 , 56 per cent . of which is Ca . The weight of thecrucible and ash of filter -paper must be accurately known and

accounted for . It is well to let the beaker or other vessel containing

the mixture of precipitate and fluid stand for some hours in a warm

place,by which filtration is rendered much more easy and thorough .

The student may be reminded that the addition of NH4C1 holds

Mg salts in solution .

Mg‘

.— Concentrate the filtrate down to one -fifth its bulk or less .

Add slight excess of sodium phosphate , and stand aside in a warmplace for some hours . Filt er , wash the precipitate well with dilute

(NH4)HO,dry

,ignite , and weigh as Mg2P3O7 (magnesium pyro

phosphate) . The Mg form s of this weight .

Phosphates — It is rarely necessary to est imate phosphates .\Vhere , however , required ,

proceed as follows:Evaporate 200 c .c . of the water to dryness . Moisten the residue

THE CHEMICAL EXAMINA TION OF WA TER

with a few drops of pure HNO3 and evaporate again to dryness,in order to render insoluble any silica that may be present . Dissolve in dilute HNO3

'

and filter . Add ammonium molybdate in'

slight excess ; keep ,if possible , in a warm place over night , and'

filter . Wash the precipitate well with hotwater, and dissolve in

ammonia . Add a few drops NH4C1 and slight excess of MgClz,and filter . Wash the precipitate thoroughly with dilute ammonia .

Dry, ignite , and weigh the Mg3P307 . The phosphates returned

in the form of P30 will be represented

'

by T7

11

1Of this weight .

It is hardly necessary to say that a qualitative test for phosphatesshould be carefully performed before entering on the more lengthyquantitative estimation . For this t est concentrate by evaporation a quantity of the water— say 200 c .c .

— to one - tenth its bulk .

To 10 in a test - tube add a drop or two of HNO 1 or 2 c .c .

solution of ammonium molybdate,and heat to a temperature

somewhat below boiling, for several minutes if necessary . A green

ish - yellow Coloration indicates traces of phosphates , a canary -yellow

colour an appreciable amount,and a yellow precipitate larger

quantities .

Silica.—This compound generally exists in water, either as

soluble silicates of the alkali es , or as insoluble Silicate of alumina .

Evaporate 300 of th e water to dryness after acidulating with

HCl . Treat the residue with strong HCI, and transfer by washing'

Qto a filter With boiling water . Dry, ignite , and repeat the fore

going treatment with acid and boiling water three or four times .Finally dry, ignite , and weigh as SiOz.

Sulphates are

'

readily detected by concentrating to about one

tenth, and adding to the warmed sample a drop of HCl and a fewdrops of BaCl2 in solution , when a white insoluble . precipitate of

BaSO4 is formed and rapidly Sinks to the bottom of the test - tube .

The i nsolubility of this precipitate should always be tested w ithsufficient strong nitric acid .

Estimati on of Sulphates - A measured quantity of the water

is heated to boiling in a beaker ; a few drops of HCl'

are added, and

sufficient hot solution of BaCl2 to precipitate the whole of thesulphates run in . T ime is given to the precipitate to settle, anda little more of the BaCl2 allowed to fall into the supernatant clear

solution . If no turbidity is produced the reaction is complete -

j


but if even the slightest turbidity occur more BaCl2 must be added ,

and the mixture again allowed to settle , until the addition of a dropo f BaCl2 produces no turbidity . The white precipitate is collectedon a filter-paper , the weight of whose ash is known

,well dried ,

ignit ed in a cru cible , and weighed as BaSOd .

The SO4 is returned as 39

36

3 of this weight .

Alkaline phosphates , sulphates , and chlorides may indicate

animal organic matter, especially urine , but it is often difficult toattribute to these salts a source in recent pollut ion , as all are foundin strata free from organic matter . Wh ere marked excess is found ,

the composition of the geological strata accurately known , and

where frequent analysis o f pure waters from the sam e strata aremade , an increase of any or all may be attribut ed to organic pollution . But it should be remembered that slight variat ion in amountof these salts is met with from time to time in waters arising incertain strata , where contamination is out of the quest ion .

Nitrites , nitrates , and po i sonous metals , when present , will befound in the dry residue forming the total solids . The metals are

most easily detected in this residue .

Poisonous Metals .

There are only a few metals whose compounds are found in

water - supplies .-Lead and copper are the chief ; occasionally iron

and zinc occur ; and very rarely chromium and tin .

A qualitative examination should be performed in all cases fo r

each of these metals ; and where a possibility of other metallic.

compounds derived from mines , industrial wastes , etc . , exists , a

further careful investigation is necessary .

Lead.— Waters possessing an acid reaction , such as those derived

from peaty moorlands , in which organic acids (ulmic , geic , etc . )are form ed by certain micro - organism s , dissolve lead . The primary

action of water on l ead is an oxidation . In alkalin e and strictlyneutral waters the coat ing of oxide remains intact , but in acid

waters it dissolves . Hard waters contain ing abundant carbonates

form an insoluble oxycarbonate ; hence hard waters lack the

property of dissolving lead . Houston distinguishes between the

solvent action of acid waters,and the erosive action of -

neutralwaters containing dissolved oxygen . Acid waters should be cut


out of public supplies , if they cannot be passed through chalk ,limestone, etc. , so as to be completely neutralized . Four parts

of CaCO3 or MgCO3 per are necessary to eliminate plumbo

solvency .

The effects of acid moorland waters on lead have been only too

clearly seen In certain districts of Yorkshire and Lancashire, wherethe inhabitants have suffered from anaemia , constipation , coli c ,wrist - drop

,depression

,gout

,renal disease , and other classical

effects o f l ead-poisoning . The lead is dissolved out of,materials

of j oints , block—tin pipes , house pipes , cisterns , etc .

-Whilst carbonates and sulphates in water diminish plumbo

solvency,nitrates favour it

,as lead nitrate Is

, the most soluble

salt of the metal . A riSe in temperature up to 48°to 50

°C . increases

plumbo - solvency .

Compounds of l ead and Copper in acid solution are precipitatedas sulphides by H2

S . [Pb ,it should be remembered, is partially

precipitated from strong solutions by HCl as chloride ] Copper is

not precipitated by HCl or soluble chlorides .

The precipitated sulphides of Pb and Cu are insoluble In (NH4)2Sand . KOH . Strongly acid solutions of these metals are not pre

cipitated completely until suitably diluted with water . Leadsulphide (PbS) , produced by adding H2

S water , or by passing H2S

gas, is black , insoluble in KOH , KCN , and (NH4)2S, but so lub

z

le

in boiling dilute HNO it is changed by boiling strong HNO3 intowhite insoluble PbSO4 .

Solutions of lead salts on addition of excess of dilute H2504 give

white PbSO4 .

K2CrO4 produces a yellow precipitate (PbCrO4 soluble in KOH ,

insoluble In acetic acid .

KI precipitates yellow lead iodide (FbI2) , more insoluble in waterthan the chloride .

Quantitative Estimation . Prepare a standard solution of

Containing gramme Pb per c .c .

The molecular weight of lead acetate is 379, of which 207 parts

are Pb . Accordingly 222, or 1 -83 1 , grammes of the salt contain

1 gramme Pb . Dissolve therefore , with - the aid of a little‘

free

acetic acid , one—tenth of this quantity 0-183 1 in' a litre of


water— and each c .c . will contain O ‘

OOOI Pb . To 100 c .c . of the water

in a Nessler glass standing on a white t il e add a few c .c . dilute

acetic a cid and sufficient H2S solution to precipitate all the lead .

To 100 c .c . of distilled water in a S imilar N essler glass add the same

amounts of acet ic acid and H28 solut ion ,and run in from a burette

or pipette the standard l ead acetate solution until the depth of tint

in the two Nesslers is exactly the same . Perform a second experi

ment , in which the whole volume of the standard lead acetate

solution is added to the acidified distilled water at once , and thenthe H28 solution added and well mixed .

The weight of Pb present in milligrammes per 100 c .c . (parts permilligramme (o -ooor gramme) x the number of c .c .

of standard lead solution used .

It may be necessary to dilute the water sample , in which case

a careful record of the amount of dilution must be made , and taken

into account in calculating the resul t . Or it may be necessary toevaporate 500 c . c . , or a litre , down to 100 c .c . , and to use this for

the estimation . Concentration may be necessary also in the quali

tatiye examination .

Not more than 0 -025 part Pb per may be present in

water without producing an effect when the water is drunk ; 00 95per has proved fatal , and 0-050 i s dangerous . In a word ,all drinking water should be free from lead , as its poisoning actionis increased through accumulation in the body .

Copper— QualitativeExam in ati on — There are two classes of cOpper

salts— cupric and cuprous . Cupric sal ts are blue or bluish - green ,and when freed from water of crystall ization become pale or losecolour . Cuprous salts are usually white or colourless ; they yield

red Cu2O when mixed with KOH , and white Cu212 when mixed with

KI solution . CuO is black ; Cu2O red .

A little dilute NH4OH added to solutions of copper sal ts produces

a greenish - blue precipitate . More NH4OH dissolves the precipitate ,f orming an intensely blue liquid .

KOH forms a pale blue precipitate , which when heated becomesblack .

H2SO4 produces no precipitate ; difference from lead .

K4Fe (CN) 3 produces a reddish

- brown precipitate , Cu2Fe (CN)insoluble in acetic acid .

THE CHEMICAL EXAMINA TION OF WA TER 33

H2S throws down a brownish - black precipitate of CuS insoluble

i n KOH, (NH4) 2S ,

in boiling dilute H2SO4 ; soluble in boiling HNO

and in KCN solution .

Quantitative Estimati on .

— Prepare’

a standard solution of copper

sulphate containing 0 3929 gramme CuSO4 ,5H2O per litre . One c .c .

of this so lution = o -0001 gramme Cu .

Dilute or concentrate the water if . necessary , and place 100 c .c .

in a Nessler glass as in the case of Pb . Add a few c .c . decinormal

acetic acid and a few drops K4Fe (CN) 6 solution ; a reddish-browntint is produced . Match

'

the intensity of this colour in a similarNessler glass by mixing the necessary volume of standard copper

solution with 100 c .c . distilled water and the same quantities of

decinormal acetic acid and K4Fe (CN) 3 as were added to the glass

containing the sample .

The number of c .c . of standard copper solution x O ° I gives the

weight of Cu in the water in parts per as in the case of Pb .

Not more than o r part per Cu is permissible in potablewater .

Tim— There are two classes of tin salts— stannous and stannic .

1 . Pass H2S into a solution of stannouS'

salt acidified with HCl:adark brown precipitate soluble in KOH and yellow ammonium sulphide forms on heating ; reprecipitated by HCl from the KOH solu~

tion as brown SnS, and from the ammonium sulphide solution as

yellow SnS2

. [Note SnS is insoluble in colourless ammonium sulphide ]2 . Add HgCl2 to acidified solution of a stannous salt:

'

a whiteprecipitate , Hg2Cl2 ; turns grey on boiling if the Sn salt is in excess

through formation of metallic mercury and stannic chlorideHg2Cl2 SnCl2 Hg2 SuCl4 .

3 . Add to the acidified stannous salt a drop of Br -water and a

little AuCl3:purple precipitate . Purple of Cassius .

’

Stannic salts in acidified solution:1 . H

2S:yellow precipitate of SnS2, soluble in both yellow and

colourless ammonium sulphide ; soluble in KOH on heating ; re

precipitated by HCl as yellow SnS2 from both solutions .2 . HgCl2:no precipitate .

3 . AuCl3:no precipitate .

Quantitative Estimati on of Tin (Stannous or Stannic) .— In a

measured quantity of water, concentrated if necessary to a small

34 PRA CTICAL SANITAR Y SCIENCE

bulk, precipitate the Sn as sulphide . Stand in a warm place till the

smell of H2S has nearly disappeared . Filter . Wash well . Dry .

Ignite in the air into SnO2. Weigh,and calculate the Sn . [Inciner

ate the filter -paper apart from the precipitate , and add the ash to

the crucible containing the SnO2.]N0 t in should be present in drinking water .

Iron .— Ferruginous waters are found in mountain limestone

,

chalk , Bagshot sands , and greensands . They are general ly opalescent, and slightly yellow in colour . The metal occurs as a

bicarbonate which is readily converted into an insoluble carbonate ,and al so oxidized into the well—known rust — hydrated ferri c

oxide , Fe2O3 , H O . Ferrous salts decompose nitrates , absorbing

O and producing nitrites , which in turn are further reduced toNH

3. This reducing action accounts for the free NH

3often found

in pure waters derived from the greensands and other strata .

Chal ybeate waters may be quite clear when drawn , but as

oxidation of the Fe proceeds they become turbid and more or lessbrown . The insoluble and highly oxidized particles dissolve on

the addition of a little dilute acid . Such turbidity m ay have itsorigin in iron pipes , cisterns , etc .

, in addition to strata .

Two classes of iron salts exist:ferrous , in which Fe is divalent , andferric , in which it is trival ent . They may be readily distinguished

by the three reagents,potassium ferrocyanide , K4Fe (CN) 3 , potassium

ferri cyanide , K3Fe (CN) 3 (a solution always being made from the crystals immediately before use) , and potassium sulpho - cyanide , KCNS .

Reage nt. Fe rro us Compound . Fe rric Compound .

K4Fe (CN )6 Light b lue precip itate ,b e Dark Prussian b lue , in

com ing d ark b lue o n oxi so lub le in HCl ; turn eddation by th e a ir , HNO3 ,

b rown by KOH .

o r B r .

K3Fe (CN ) 6 Dark b lue precipitate ; N 0 precip itate .

Turnbull'

s b lue inso lub le

in HCl .

KONS N o red co lour . Blood—red co lour (no pre

cip itate ) . Co lour d e

stroyed by dropping a

few d rops into a so lut ion

OfH gClz.


Chrorhium .~ -Evaporate a litre of the water to be tested to

dryness , and fuse the ash with solid potassium nitrate and sodiumcarbonate to produce yellow K2CrO4 , which , in neutral solution .

produces a red precipitate with AgNO3 (soluble in ammonia anddilute nitric acid) , and in . solution in acetic acid gives a yellowprecipitate wi th lead acetate insoluble in dilute acetic acid . A few

c .c . of a largely concentrated sample may be dropped on a thin layer

of ether which has been floated on a dilute solution of H202 acidi

fied with H2SO4 . Upon slight agitation the blue colour which

forms in the lower solution passes to the ether .

In chromates (yellow or red in colour) Cr exists in combination

with oxygen , acting as an acid radicle . Cr also forms a set of salts

in which it acts as a metallic radicle . These are green or Violet incolour, but pass through oxidation into chromates .

Conversely,chromates pass by reduction into green chromic

compounds . Acidify a chromate with HCl , add Zn , and warm ;the yellow chromate passes into a green chromic salt .

(NH4)OH and KOH in small quantity produce a pale bluishgreen or purple precipitate ofCr2(OH) 3 , more or less soluble in excess

of the precipitant .

Quantitative Estimati on — A chromate is first transformed by areducing agent into a chromic salt . A solution of the chromic saltis then precipitated by NH4OH in presence of NH4CI, and the

resulting hydrate converted by ignition into Cr2O3 . and weighed.

From the weight of Cr2O3 the amount of Cr i s calculated .

No chromium should be present in a drinking water .

Zine — Concentrate the water .

(NH4)2S produces a white , flocculent, gelatinous precipitate ,which often appears yellow owing to excess of yellow ammonium

polysulphide , (NH4) 2Sn . This reaction is characteristic , as zinc

sulphide is the only white sulphide capable of being precipitated .

Zn is only partly precipitated from neutral solut ion by H2S, but by

adding sufficient NaOH , NH4OH , or sodium acetate , the whole of

the metal may be precipitated by this reagent .

Solution of NH4OH gives a white precipitate of Zn , (OH) readilysoluble in excess of ammonia .

K4Fe (CN) 6 produces a white gelatinous precipitate of zinc ferro

cyanide .

THE CHEMICA L EXAMINA TION OF WA TER 37

Quantitative Estimati on of Zn .— Prepare a standard solution of

ZnSO4 ,7H2O. In 287 parts of this salt there are 65 of Zn , or in

4 4 parts I of Zn . Dissolve grammes of the crystals in a litre

ofwater (each 0-001 gramme Zn) . Use this standard solutionvolumetrically, as in the case of Fe, precipitating the Zn withK4Fe (CN) 3 . Avoid much excess of the ferrocyanide . This may be

effected by placing a drop of the mixture on a white tile in contact

with a drop of a saturated solution of uranium acetate , when a

brown colour appears immediately free ferrocyanide is present .

Gravimetzic Estimati on — Heat a measured quantity of the con

centrated water to boiling, and add slight excess of a solution of

Na2CO3 . Boil again , and allow the precipitate to settle . Was h

several times by decantation with boiling water ; transfer the pre

cipitate to a filter, and finish the washing thereon . When finished

the wash-water shows no alkalinity to litmus and gives no precipi

tate with BaCl2.

Dry the precipitate, and carefully transfer it to a porcelain cruci

ble . Heat to redness . Wet the filter—paper with strong ammonium

nitrate solution , and dry it ; incinerate it in the flame in a coil of

platinum wire , and let the ashes fall into the crucible . The flame

should not enter the interior of the crucible during ignition ,lest

reduction of the ZnO take place . Cool and weigh . Calculate Zn

from ZnO

Carbonate of Zn , ZnCO3 , is found in certain mineral waters in

quantiti es varying from 00 01 to 0 005 parts per As

much as 10 parts per ZnSO4have been detected in such

waters . Zinc may be introduced by galvanized iron tanks or pipes .It should not be found in a drinking water .

CHAPTER IV

ORGANIC MATTER IN WATER

AS vegetable organic matter has little significance from the sanitarypoint of view, attention is almost entirely directed to animal matter

in the form of sewage . It is not proved that animal organic matter

per se in the quantiti es found even in dilut e sewag e is hurtful tohealth ; its importance li es rather in the fact that pathogenicmicrobes , especially those of intestinal origin

,accompany it .

Wherever , then , faecal matters in quantity large or small are met

with danger exists .

The complex remains of dead animals and plants are slowly

chang ed to simple inorganic compounds in the superficial layers ofthe soil under the action of manifold ferments

,the products of

micro - organisms in association with favourable quantities of heat ,moisture , and oxygen . The sum total of these changes is spoken

of as an oxidation,since the end products are/oxides of carbon ,

nitrogen , etc but there is no doubt that as in the case of the variousferrnentations which take place in the alimentary canal of animals ,known collectively as digestion

,reductions frequently alternate

with oxidat ions . There is some evidence to Show that these ferments , metabolic products of aerobic and anaerobic bacteria , act

along certain lines which are intimately correlated . The specific

action of one enzyme furnishes the necessary conditions for theoppos ed functions of a succeeding enzym e .

Whilst an accurat e qualitative or quantitative estimation of

organic matter in a potable water is impossible , still there arecertain chemical t ests of value in directing us towards the source

of the organic matter,which source may ultimately be discovered

by other means .

A rough differentiation of anima l from vegetable matter may be3 8

ORGANIC MA TTER I N WA TER 39

effected by a consideration of the ratio of organic carbon to‘ organic nitrogen ,

’ which ratio forms the basis of Frankland’

s

well - known method of estimating organic matter . The process i s

only suitable for experienced chemists and laboratories equippedwith apparatus for gas analysis . But in skilled hands it is simple

and direct . A measured volume of water is carefully evaporated

to dryness ; the residue is introduced into a hard glass tube along

with some oxide of Copper, and the tube is heated in a furnace

until combustion of the organic matter is complete . The gaseous

products of combustion— carbon dioxide , nitric oxide , and n itrogen-are severally collected and weighed , as organic carbon and

organic nitrogen .

’ If insurface waters the proportion of organic

carbon to organic nitrogen be as low as 3 I‘

the organic matter

may be considered as of animal origin , whilel

if it be as high as

8 1 it is chiefly vegetable . In certain fresh peaty waters the ratio

of C N has been found as high as 12:1 . In fresh sewage the

proportion of C N may be 2 1 . Frankland held that the smaller

the proportion of organic carbon and organic nitrogen in a water ,and of these constituents the larger the proportion of C N ,

other

things being equal , the better is the quality of the water .

The ferm entation of dead organic matter , known as putrefaction ,’

is effected by many types ofmicro - organisms .

Dead proteins are hydrolysed to proteoses ; these to peptones ;peptones ti) amino - acids ; finally amino—acids are split

,evolving

ammonia .

“

If we follow this ammonia as it escapes,say, from a dung-heap

in solution into the soil, we shall find that in the presence of the

nitrous organisms nitrous acid is formed , which in contact with

the bases of the soil rapidly becomes nitrites . Later,through the

activiti es of the nitric group of micro - organisms, nitric acid is

generated,which speedi ly becomes n itrates . These various stages

in the oxidation or pur ification of nitrogenous matters stand out as

chemical landmarks , and present considerable information to the

water analyst .

As carbohydrates and fats are much less complex bodies contain

ing C, H, and 0 only, their decomposition and oxidation ar e much

more simple:carbon is burnt to CO2, and H to H2O .

These changes in nitrogenous matter may be studied dir ectly .

o PRA CTICA L SANITAR Y SCIENCE

If , for example , A be a source of organic pollution , say a manure

heap,on the surface of the ground ,

and B , C,D , and E wells at

increasing distances from it , analysis will Show that the water inB contains abundance of NH nitrification has not yet taken place .

At C the oxidation processes have advanced to the stage of nitrous

acid ; this water will contain less ammonia and some n itri tes . The

water from D has travelled farther,encountering more nitrifying

organisms,with the result that ammonia has disappeared

,and nitrites

and nitrates are found . At E purification is complete— the whole

of the N is oxidized to nitric acid ; hence this water contains noNH

3 ,no nitrites

,but only nitrates .

The opportunities for purification offered between A and B are notsuffici ent to carry the oxidation changes beyond the stage of NH3 ;

whereas the j ourney from A to E is of such length that the entire

NITRATE

FIG . 3 .

changes have been completed . At intermediate points are observed

int erm ediate stages in the purification .

From the consideration of a single instance of this kind,no con

elusions as to the distance a well must be removed from a source

of contam ination in order to be safe can be drawn ,since the factors

in the problem of safety are numerous and variable . The distance

between A and E, if the water in E is to be completely purified ,would require to be much greater if the slope from A to E be considerable , or E would need to be much deeper . On the otherhand , i f the slope of the ground water descended from E to A, it

is possible that the water of B may be free from all organic matter .

The porosity of the soil , conditions of heat and moisture necessary

to Vigorous growth of purifying organisms , direction of slope o f

ground water, geological features of subso il and underlying strata ,rainfall , and a number of other factors , all influence this questionof safe distance of well waters from foci o f contamination . Each

case must be worked out on its own merits ; and here the chemical

ORGANIC MA TTER IN WA TER 4 1

examination renders useful service . A sample of water from E

may be pure to - day— that is,contain no organi c matter as such ,

no NH3 ,no nitrites , but only nitrates ; to -morrow, owing to increased

rainfall,whereby more organic matter than usual is washed into

the soil, or to some other condition by which the powers of the soil

for purification are lessened , this same water may contain , besides

nitrates , nitrites , NH3 ,and even undecomposed organic matter .

It should ever be borne in mind that the machinery by which

organic matter is purified in the soil is liable at any point to break

down,and in too many instances although just sufficient for the

work is near breaking-point . The question ,therefore, should be ,

not how near to a focus Of contamination may it be safe to procurewater, but rather how far from the focus is it possible to acquire

it. Chemical analysis, it frequently and regularly performed , will ,in most cases , discover such breakdown in the purification

machinery, although a single analysis , unaccompanied by further

information as to source and surroundings , may be quite useless .

It is the comparative information regarding a water acquired by

sv stem atic and repeated analyses that is of value .

The student should note that the nearer the nitrogenous organic

matter of dom estic sewage stands to the stage of raw proteins

the worse, as it is in this stage that pathogenic bacteri a are found

in their most toxic and vigorous condition ; and that , conversely ,

the farther “from this stage such matter stands the less dangerousit is . When organic matter reaches the stage of nitrates no pathogenic germs will live in it .

From the standpoint of infection , fresh faecal matter and urine

are the most dangerous of all forms of organic matter .

It is not possible in water analysis to separat e and estimate rawproteins , proteoses , peptones , and amino—acids . The next stage

,

that of NH3 ,l ends itself to ready estimation .

When this free and saline ammonia , as it is called ,is removed

,

the remaining organic matter, which consists of the nitrogenouscomplexes constituting the antecedent stages , can be rapidly

oxidized by the aid of a powerfIIl oxidizer and heat (Wanklyn’

s

process) into ammonia , and estimated as albuminoid ’ ammonia .

This figure, inasmuch as it measures those portions of the nitrogenous organic matter likely to contain pathogenic micro—organisms

,


is obviously the most important determination connected with this

portion of the subj ect .

Estimation of Free and Saline’

NH3 .— Prepare a standard

solution of (NH4)CI, 1 c .c . of which : 00 1 milligramme NH3.

53-

5 grammes NH Cl contain 17 grammes NH3.

3-14 1 gramme NH

3.

Dissolve 3 -14 dry anhydrous I'

H4Cl in 1 litre ammonia - freedistill ed water . One c .c . of this solution: 1 milligramme NH3 .

This is too strong . Dilute 10 c .c . of it to a litre ; 1 c .c . now = 0-01

milligramme NH3

.

The process depends on the fact that when the water is distilledwith a little sodium carbonate all the ammonia in the water , free or

combined,passes over in the first portions of the disti llate , and may

be estimated by N essler’

s solution .

Prepare Nessler’

s solution . Dissolve 62 °

5 grammes KI in about

250 c .c . distilled water . Set aside a few c .c . of this solution . Now

add to the larger portion saturated mercuric chloride solution till

precipitated mercuri c iodide ceases to dissolve on stirring . Add

the reserved KI so as to redissolve the precipitate,and again add

cautiously sufficient mercuric chloride solution to produce a slight

permanent precipitate .

Dissolve 150 grammes KOH in about 300 c .c . water ; cool ; add

gradually to the above solut ion ,and make up with H2

O to a litre .

A brown precipitate settles out on standing , and'

the supernatan tfluid is clear and of a pale greenish - yellow colour . I t is ready for

use as soon as it is perfectly clear . It should be decanted withoutstirring up the sedim ent . Keep in bottles closed with well—fittingrubber stoppers . This solution is rendered sensitive from time to

time by the addition of a little more HgCl2 solution ; its sensitivenessdepends on its being saturated with HgCl2.

S odium Carbonate — Heat anhydrous Na2CO3 to redness , taking

care not to fuse it ; transfer to a mortar , and grind to a fine powder .

Store in a clean , dry, wide -mouthed,stoppered bottle .

Arnmonia - free water is prepared by distilling ordinary water in

the presence of Na2CO3 or H2

SO4 , and rej ecting the first portions of

the distillate until there is no trace of colour produced on N esslerising

50 c .c . of it .

44 PRACTI CAL SAN I TAR Y SCIENCE

a few minutes the yellow colour wi ll have fully developed , and it sdepth can be gauged by looking down through the column . Should

there be some discrepancy in the tints , rapidly add to anotherNessler glass containing distilled amm onia- free water a little more

or a little less of the standard solution , as the case may be , unti l

an exact m atch is produced . In all such colorimetri c work every

condition should be exactly similar in the two cases— length of

time reagents are in contact , order in which reagents are added .

Shape and size of containing vessels , etc . The standard solutionof NH

4C1 must be added to the second Nessler glass before theNessler

’

s reagent , as this occurred in the Nessler glass containingthe dist illate . If the standard solution be added after the Nesslerreagent an Opacity is likely to form which prevents to some degree

an exact match being made . Several trials m ay be necessary beforean accurat e result is reached .

The second and third 50 c .c . of the dist illate are treated in thesame way , and the sum of the results in terms of c .c . of the standard

solution noted .

Wanklyn found that the whole of the free and saline NH3was

contained in 150 c .c . distillate , and that the first 50 c .c . contained

three - fourths of the total .N essleris e the second dist illat e first

, and note whether more than1

°

5 c .c . of the standard NH4Cl solut ion is required to match it . If

so , the first distillat e must be diluted before Nesslerisat ion , otherwise the colour will be too intense to be accurately matched .

Example .

First N essler glass m atch ed by 3 -00 c.c NH4CI (1 c.c.=0 -0 1 m illi gramm e NH 3 )

Second 0 -

75Thi rd 0 25

To tal NH3=But each c.c. standard NH4Cl= o -01 mi lligramm e NH

4

And in 500 c.c. o f the w ater under exami nation there is 0 -0 4 m i lligramm e NH3 .

In 100 c.c. th ere w i ll b e 0 -008 m i lligramm e NH3 , or ,S ince 100 c.c. w ater=

m illigramm es , th is w ater contain s free and sa line NH3 to the extent o f0 -00 8 part per

Estimation of ‘Albuminoid’

NH3 . Whilst the Nesslerisat ionof the free and saline NH

3is going on , 50 c .c . of alkaline potassium

permanganat e (composed of 200 grammes KOH , 8 grammes per:

ORGANIC MA TTER IN WA TER 45

manganate,a litre o f water) should be boiled , so as to expel any

ammonia that it may contain,and to heat the liquid in order to

prevent cracking the retort when pouring it in . This is a strongly

oxidizing reagent,and rapidly converts undecomposed organic

matter into NH3. By this moist combustion process a degree of

oxidation is effected in the course of half an hour or so in the

laboratory that would require weeks or months by the natural

processes outside .

When the alkaline permanganate is ready ,the cork of the retort

is removed and the hot solution poured in .

This portion of_

the distillation should be carried out more slowly,as organic matter is slowly decomposed, and the distillat e should

be collected as long as any NH3comes over . No relation exists

between the number o f the N essler glasses collected and the totalNH

3 ,as in the case of the free and saline portion . Moreover , the

second Nessler may contain as much NH3at times as the first .

The student should fit up his apparatus himself, and see that

all connections are water - tight and gas—tight,as the case may be .

Corks Should be carefully bored and made to fit flasks and con

denser tubes , and indiarubber corks are preferable to wood . The

dist illing - flask should be thoroughly cleansed with weak acid and

rinsed out with distilled water until all traces of acid have di s

appeared . It is well to distil some pure ammonia - free water

through the condenser In order to get rid of any traces of NH3

that it may containbefore starting the distillation of a sample . A

large and constant stream of water running through the condenser

is necessary throughout the entire process . A long—stem funnelis to be used for delivering water

,etc . , into the retort , and this is

e specially necessary for the introduction of the hot alkaline permanganate, so that none of the reagent may enter the central tubeof the condenser and foul the distillate .

Seeing that the atmosphere of an ordinary chemical laboratorycontains quantities of NH

3 ,it is well to have a separate room for

water analysis .

In very rare instances a potable water may not yield the ent irefree and saline NH

3to the first 150 c .c . of the distillate . In such

cases it will be necessary to distil over and Nessleris e a fourth or

fifth 50 c .c .


It is'

possible that the saline ammonia exists in water in con

j unct ion with some acid , which , on being boiled in the presence

of carbonates , yields up the ammoni a in the form of (NH4)2CO3 .

In the second part of the process , the distillation of the albu

m ino id ammonia may require to be carried to a point at which

the volume of fluid in the flask becomes dangerously small ; thisShould never be allowed

,but ammonia - free distilled water Should be

added to the flask as required, so that the volume may be kept up .

With regard to the amounts of free and saline and albuminoid

ammonia which may be allowed in different potable waters , there

is some little difference of opinion . All observers agree that the

two ammonias must be considered together,and most agree that

in drinking waters if the albuminoid reach 0-005 part per

the‘

free and saline Should not be more . I f the albuminoidbe small— say less than 0 002 part per — the ‘ free and

saline may be allowed to slightly exceed 0 -005 .

Much‘

albuminoid and little free and saline ammonia indicate

vegetable matter ; whereas much free and saline and little album ino id indicat e animal matter . These indications must not betoo lit erally reli ed upon .

As a general rule, it may be stated that where a water has been

contaminated with sewage the high ‘ free and saline ammonia

figure will be supplemented by an increase in chlorides,phosphates ,

and oxidized nitrogen . Whilst accepting the principle that animal

pollution is indicated by a relative ly larger figure for ‘ free and

saline ammonia than for albuminoid,

’ and that vegetable matter

produces much albuminoid ammon ia , with little or no‘

free ,’

it must be borne in mind that these relations are liable to be upset .Peaty waters , whilst producing albuminoid ammonia in quantity ,

should not produce any ‘ free still,there are peaty waters met

with at times which give rise to a small quantity of free ammonia ,although no animal matter can be traced .

Good Spring waters rarely contain albuminoid ammonia above0-002 part per Upland surface wat ers , as a whole , should

not produce‘

free and saline ’ ammonia .beyond 0 001 part per

The degree of initial dilution necessary to produce the best

colour- tint for matching on N essleri sation can only be discovered

ORGANIC MA TTER I N WA TER 47

by experience,and here , as in all matters practical , the student

Should ever appeal to experiment . Scores of waters must be

patiently worked out in complete detail before he can expect to

acquire even an elementary knowledge of the subj ect .

Much free and saline ammoni a in the absence of albuminoid

may be accounted for by the water passing through strata rich in

ammonium salts,portions of which are carried away in solution ;

water -bearing strata containing nitrates and subsalts of iron afford

free and saline ammonia by the reduction of the nitrates through

the intermediate phase of n itrous acid to NH3 ; rain water falling

through the atmospheres of towns abounding in ammoniacal fumes

w-ill yield appreciable quantities of‘ free ammonia , and at times

small quantities of albuminoid also from the organic matter in

suspension in the air .

It may be noted that,although the Wanklyn process does not

decompose urea , the most important and abundant nitrogenous

constituent of urine, nor recover NH3from a few other bodies in

sewage , still it is of the greatest value in dealing with the contam ination of water by organic matter

,from the comparative

results afforded,so long as the determinations are carri ed out

under Similar conditions .

Oxidizable Organic Matter in Water .

Forchamm er applied to water analysis his knowledge of the ex

perim ental fact that organic matter in the presence of an acid can

rob K2Mn

2O8 of a portion of its oxygen . This process was S lightlymodified by T idy, and is usually known in this country in connection

with his name . It is not a reliabl e test of either the quality or

quantity of organic matter present,but

,in that pure waters absorb

practically no O from permanganates of potassium,and foul waters

a great deal, the process has some value as corroborative evidenceof the presence of organic matter . It should be noted that other

bodies beside organic matter,such as ferrous salts

,nitrites , sul

phides , etc . , abstract O from K2Mn

203 , and when these are presentthey must be accounted for before drawing a conclusion as to the

amount of organic matter dealt with . The quantity of O absorbed


varies with the time Of contact , the temperature , and , to less extent ,with the acidity, and light admitted during digestion .

Potassium permanganate in contact with organic matter and

H2SO4 furnishes 5 atoms of O and colourless sulphates ofmanganeseand potassium .

K2Mn203 3H2SO4 2MnSO4 K2SO4 3H2O 50 .

If sufficient acid be not added, the hydrated peroxide falls as an

Opaque brown precipitate , and only 3 atoms of O are set free .

K2Mn2O8 H2SO4 3H2O 2Mn (OH)4 K

2SO4+ 30 .

During the digestion the reaction should be carefully watched ,to see that the fluid remains transparent throughout . If much

organic matter be present , it may be necessary to add further quantit i es of permanganate from time to time .

Various times and temperatures have been employed in this

process for digesting the sample of water with the acid and per

manganate, some analysts recommending four hours at 80°F. ,

others three hours , two hours , or fifteen minutes , at higher and lower

temperatures . In a laboratory where an incubator is kept at

blood - heat (37°C .) it is convenient to use it , and three hours is a

suffici ent length of time . In examinations two hours at room

temperature may be found most convenient .

Prepare a standard solution of potassium permanganate (1 c .c

milligramme of available O) by dissolving 0 -

395 gramme of the

pure crystal in a litre of distilled water . Make a fresh 10 per

cent . solution of KI , and a fresh solution of sodium thiosulphat e ,of about 1 gramme to a litre of water . Lastly, prepare a boiled1 per cent . solution of starch

,and test its delicacy with water con

taining the merest trace of free iodine .

Clean two Erlenmeyer flasks (capacity 150 c .c . or less) , and intoone measure 100 c .c . of the water sample . Mark it Sam ple with

a wax pencil . Into the second,marked Control ,

’ measure 100 c .c .

distilled water . Now carefully pipette into each 10 c .c . of the

standard solution of K2Mn

2O3 , and with another pipette run into

each 10 c .c . of a 25 per cent . solut ion of pure H2SO4 . Stopper andset aside in an air oven or incubator, as the case may be , at 37

°C .

for a period of three hours . Should the amount of organic matterin the water be large , the whole of the permanganat e may be de

ORGANIC MA TTER IN WA TER 49

composed and become colourless ; in such a case a second 10 c .c . of

the standard solution is added,and Should this be decolourized a

third, and so on . Account of the further additions will be taken

in the calculation at the end of the experiment .

When the time allowed has expired, and a portion of the per

manganate remains undecomposed,as demonstrated by the red

tint still to be seen , a few drops of the K1 solution are added to the

flask containing the water sample , when free iodine is liberated in

quantity proportional to the amount of undecomposed K2l\-In

2O8

remaining . A very few drops of the KI solution will contain an

excess of iodine . This liberated I— the measurer of the undecom

posed K2Mn

2O8 left in the Erlenmeyer— is made to oxidize thio

sulphate run into it from a burette,the end reaction being definitely

ascertained in the presence of a few c .c . of the boiled starch solution

by the disappearance of the blue colour of the iodide of starch .

The same procedure exactly is carried out with the control, and

here, as no K2Mn2O3 has been decomposed, but the whole of the

10 remains intact , we obtain a figure in terms of c .c . of thio

sulphate solution which represents this amount , or 1 milligramm e

available O .

The followmg equat ions represent the liberation of free I and

its subsequent oxidation of sodium thiosulphate to sodium tetrathionate

K2Mn

2O3 I OKI 8H2SO4: 6K2

SO4 2MnSO4 8H O 5I2 .

I2 2Na

2S2O3 : 2NaI Na

2S4O3 .

Example — The intact 10 c .c . standard solution of permanganate

in distilled water liberated iodine equivalent to 27 c .c . of the thiosulphate solution . The un decomposed portion of the 10 c .c . of

standard permanganate in the water sample liberated iodine equiv al ent to 23

-2 c .c . of thiosulphate . From this it is plain that the

amount of permanganate solution decomposed by the organicmatter (assuming that n o nitrites , sulphides , etc . ,

were present ) isrepresented by 27

—23-2 c .c . thiosulphate . But 10 c .c . standard

permanganate or 1 milligramme O: 27 c .c . thiosulphate ;

27 27—23

-2 1 milligramme x ;

0 -14 .

50 PRA CTICAL SANITARY SCIENCE

There is , therefore , in 100 c .c . of this water organic matter capable

of absorbing from perm anganate of potassium O to the extentof 0-14 milligramme , or 0-14 part per under the conditions

of time and temperature employed .

I f it be desired to Obtain some indication of the nature o f thereducing substances , two samples of the water may be treated with

the standard perm anganate , one at 37°C . for fifteen minutes , and

the other for three hours at the same temperature . Nitrites , ferrous

salts,and sulphuretted hydrogen effect reduction almost imme

diately,whilst a relatively large amount of ordinary organic matter

reduces the reagent only aft er a considerable time .

The O absorbed from perm anganate is higher as a rule in uplandsurface waters than in waters from other sources ; and wh ilst no

strict standards can be insisted on , it may be stated generally thatin upland surface samples of great purity this figu re in parts per

(time three hours , temperature 37°C . ) will not exceed 0 -1 ,

in waters ofmedium purity 0-

3 , and in waters of doubtful purity 0 -

4 .

The corresponding figures for other sources will not exceed 0 -05 ,

0-15 , and 0-2


purificat ion may be chemically , should ever be allowed to come

In contact with drinking water . In all waters possessing a high

nitrate figure this possibility of the presence of purified sewage

should be born e in mind .

W'

hen nitrates,which form the end of the purification of organic

matter,occur alone it is obvious that no indication of the date

of the previous pollution .is given .

In determining the true significance of nitrates in potable waters

it is necessary to consider (1 ) whether they arise from geologicalstrata (chalk ,

lias , oolite , sandstones) through which the water haspercolated

,in which case the evidence of organic pollution supplied

by the other steps of the analysis— such as the free and salineNH

3 ,albuminoid NH3 ,

0 absorbed from permanganate of potassium , etc .

—will be negative ; (2) whether they are due to purifiedsewage

,in which case the quantity will be much too great

,as also

that of Cl ; (3 ) whether they represent a small am ount of organicmatter that has undergone complete oxidation , and is to be con

sidered harmless . In this case the quantity will be small— in rain

and upland surface waters not exceeding 0 -1 part per — and

all the other items of the analysis employed to discover organic

matter w ill afford negative evidence .

In the few cases where strata alone contribute soluble nitrates

the quantity will rarely exceed 0-

5 part per but no figures

can be laid down as an accurate standard , and each case must be

worked out in connection with the rest of the analytical data .

In a few instances strata containing nitrates (in particul ar thelower greensand) contain also reducing minerals , such as protosalts of iron

,which reduce HNO3 t o HNO2, and the latter to NH3

.

The same reduction can be effected by denitrifying micro - organisms .

Free NH3 , due to reduction of nitrates and nitrites , will be identifiedby the absence of organic NH3 ,

and all other evidence of organic

pollution .

N itrites are very unstable, and in the presence of available Orapidly become nitrates . In the early stages of the oxidation of

large quantiti es of animal organic matter they are mostly found incompany with NH

3 ,but a foul water may at a particular mom ent

fail to furnish any nitrites . They are significant of recent con

tam ination ,except in those cases j ust mentioned , where they are

OXIDIZED NITROGEN- NITRITES AND NITRA TES 53

due to the reduction of nitrates in strata . Nitrites , then , which

in deep -well waters may be merely the products of reduction ofnitrates by iron in strata, iron pipes , etc . , and consequently quite

harmless,will in shallow wells and surface suppli es condemn the

water .

All the inorganic N— apart from strata- found in nitrates,nitrites

,free and saline NH

3 ,after deducting that present in rain

water,may be regarded as due to previous sewage contamination .

Detection and Estimation of N'

itrItes.

Potassium Iodide and Starch — To 10 c .c . of_the water in a

test - tube add 1 c .c . of a clear and boiled 1 per cent . starch solution

and a drop of KI solution . Mix and add a little dilute H2SO4 , when

immediately a blue colour is produced if nitrites be present in con

siderable amount . On standing, nitrates give this reacti on also

Pure sulphuric acid should be used, and it is found that , owing to the

in stability of KI, Zn I gives better results . This test can be made a

quantitative colorimetric one by Operating on 100 c .c . of the water

in a N essler glass,and in a second Nessler 100 c .c . of a mixture of

distilled water and the amount of a standard nitrite n ecessary to

form a colour match . When the proportion of nitrites in a sample

is 1 in the blue colour iS formed in a few minutes ; when

1 in in twelve hours ; and when 1 in

in forty- eight hours . Lintner’Ssoluble starch should be used .

Griess’

s Method . Make a 5 per cent . solution of meta

phenylene- diamine in water . Decolourize with animal charcoal ,

and'

render slightly acid with H2SO4 . MIIch acid must not be

used . To 100 c .c . of the water to be tested in a Nessler glass add1

'

c .c . of the reagent,cover

, and set aside in a warm place for twenty

minutes . A yellow to orange colour is produced, according to the

quantity of nitrites present . The reagent should be made at the

time of use . Whenmetaphenylene—diamine (diamido—benzol) reactswith n itrous acid, triam idO - azo -benzol (B ismark brown) is produced ;hence the colour .

2C3H4 (NH2)2 HNO

2C6H4 (NH2)N .C

3H3 (NH2)2N 2H

2O .

By using a standard solution of potassium nitrite, the co lourproduced in the 100 c .c . of water may be matched in the same

54 PRA CTI CAL SAN I TARY S CIEN CE

quantity of distilled water . A series of trials must be made , in

which the reagent is added to the contents of the two cylinders atthe same moment , and the cylinders covered and set aside in a

warm place for twenty minutes . The standard nitrite is prepared

thus:Dissolve 04 06 gramme of AgNO2 in boiling water ; add slightexcess of KCl . Silver chloride is formed , and gradually falls to the

bottom . Make up to a litre and allow to settle . When clear ,decant off the supernatant fluid , and dilute each 100 c .c . up to alitre . It should be kept in the dark and in small bottles filled to

the stopper , so as to protect it from the air .

I c .c .= 0-01 milligramme N

203

.

00 06 NO x 0 °or

00 037 x o -or

Detection and Estimation of Nitrates.

Brucine Test — To I O c .c . of the water in a test - tube add 1 c .c .

of a saturated solution of brucine , and shake . Incline the test - tube

and pour down the side 2 c .c . of pure HzSO4 . Carefully bring

the t est - tube to the vertical against a white ground . A pink zone

is formed at the junction of the acid and supernatant mixture ,which lasts for a few seconds , and then changes to brownish yellow .

When nitrates are in large quantity, the colour changes very rapidly .

Where the reaction is doubtful, a fresh layer of the mixture can bebrought in contact with the acid by imparting to the test - tube a

slight centrifugal mot ion .

Or, I O c .c . of the water may be evaporated to dryness in a platinum

dish , a drop of pure HZSO4 added, and a small crystal of brucine

dropped on the contents, when a pink colour will appear , even where

the quantity of nitrates is so small as 0 01 part per

Diphenylamine Test— Mix about I O milligrammes of diphenyl

amine with r c .c . pure HZSO4 in a porcelain basin , and carefully

run 4} c .c . of the water over the mixture . A blue colour developsin the presence of nitrates ; the depth of the tint is roughly propor

tional to the amount of nitric acid . This reaction is not simulated

by any other constituent of potable waters .

OX IDIZED N ITROGEN— N ITRITES AND N ITRATES 55

Ci’um ’

s Quantitative Method.— This method consists in shaking

up the residue obtained from the concentration of a measured

quantity of the water with metallic mercury and pure H2504 ,

when nitric oxide is produced, which is afterwards conducted to agas analysis apparatus and measured . It requires some experiencein collecting and measuring gases

,but in the hands of a skilled

operator is one of the most exact methods known . The nitricoxide produced represents the N of nitrites and nitrates . To

obtain the N due to nitrates alone, that obtained for nitrites bVGriess

’

s method is subtracted from the total . This method may beused for the estimation of nitrous and nitric N in sewage effluents .

Process of Estimation .—Evaporate to dryness in a dish 100 c .c .

of the water . Add a small quantity 25 per cent . HzSO4 . Heat the

dish to remove CO2 from any carbonate present , and if the volume

of the liquid exceeds 2 c .c . evaporate down to'

that volume . Fill

the nitrometer with Hg , and pour the contents of the dish into the

cup of the nitrometer, rinsing out with a very small quantity of

the dilute H2804 . Now run the liquid through the stopcock

,

taking care that no air enters . Run through also about twice thevolume of pure concentrated H2

SO4 , and shake so as to cause partof the Hg to mix with the hot liquid .

'

In a short time NO will be

liberated . Continue the shaking till gas ceases to come off (five toten minutes) . Cool to the t emperature of the air . Adjust mercury

levels , and take the reading . Note atmospheric temperature and

pressure , and calculate weight of N in volume of NO obtained .

An estimation gave 2 c .c . NO ; t emperature 18°C . ; pressure

758 millimetres .

291 x 760

As“

NO contains half its volume of N ,and weight of 1 c .c . H

1 8 7 x o -oooo89 x 142

gramme: 1 -165 part per N in the water .

From this subtract the weight of nitrous N found by Griess ’

s

method ; the remainder is that due to nitrates .

Copper-Zine Couple Method — This method estimates nitrousand nitric N as NH3

. In calculating the nitric N ,it is plai n that

from the 'amount of NH3 obtained in the process deduction must

gramme, the weight of N in the NO:

56 PRACTICAL SAN ITAR Y S CIEN CE

be made for original NH3in the water as well as that derived from

nitrit es .

When zinc is immersed in CuSO4 solution , a spongy deposit of

Cu is precipitated upon it , and in this condition it is capable of

bringing about various decompositions in which H is liberated .

The H is occluded by the spongy copper, and when thus occluded

reduces nitrates to n itrites , and nitrit es to ammonia . The reaction

is hastened by the presence of traces of NaCl and other salts , rise

of t emperature, and any condition which increases the electrolytic

action of the couple .

Take a piece of clean zinc - foil and cover it with 3 per cent .

CuSO4 solution until a c0pious, firm ly- adherent coating of black

spongy Cu has been deposited . This deposit ion should not be

pushed too far , otherwise the Cu will be so easily detached that it

cannot be washed . When sufficient deposit has accumulated, theCuSO4 solution is removed and the couple carefullv washed with

distilled water,when it is ready for use . A clean , wide—mouthed .

stoppered bottl e is selected and washed out with some of the waterto be tested . The coated foil is inserted , and a measured quantity— say 100 c .c .

— of the water poured in so that the foil is completely

covered . The bottle i s tightly stoppered and set aside in a warm

place for some hours . If the bottle be properly closed,the tempera

ture may be raised to 28° or 30

°C . without fear of losing NH3

.

When it is desirabl e to hasten the reaction , a little NaCl may be

added to the water (0 1 gramme to 100 or CO2 may be passed

through the water before it is placed in the bottle . In calcareous

waters lime may be removed by the addition of some pure oxali c

acid previous to digestion with the couple . N itrous acid remainsin the solution until the reaction is complete, so that it is necessaryto test a small quantity of the water from time to time by Griess

’

s

reagent for the presence of this body . Metaphenylene-diamine

easily detects 1 part of nitrous acid in of water . When

the last trace of nitrous acid has disappeared , the water is poured

off the couple into a clean , stoppered bottle , and if turbid allowed to

subside . A portion o f the clear fluid, diluted if necessary according

to the degree of concentration of the nitrates in the water , is transferred to a Nessler glass and the NH3 estimated in the usual m anner .In the case of coloured waters , or those containing magnesium and

OX IDIZED N I TROGEN ; N I TRI TES AND N I TRATES 5 7

other salts that interfere with the Nessler reagent , a measured

quantity of the water poured off the couple should be put in a

retort,a little Na

2C03 added, and Nesslerisation performed on thedistillat e . It has been found that about half a square decimetre of

zinc - foil should be used for each 100 c .c . of a water containing

5 or less parts of nitric acid per A larger proportion of

foil should be used for waters richer in nitrates and for sewage

effluents . The couple , if carefully washed after use , may be used

for at least three estimations . It is convenient in most laboratori es

to digest overnight . Where accurate results are required , andin the hands of the inexperienced

,it is advisable to distil the water

removed from the couple and estimate the ammon ia in the dis

tillate . From the total N found as NH3deduct that due to inorganic

NH3found byWanklyn

’

s process , and that due to n itrites found by

Griess’

s process ; the remainder is the N due to nitrates in the

water .

Spreng'

el’

s Phenol Method — This is a much less accuratemethod; (error of under—estimation) , but can be performed in alimited time . It estimates the N of nitrates alone, and is chiefly

applicable“ to waters containing smal l quantiti es of nitric acid .

When phenol sulphonic acid reacts with nitric acid,picric acid

(trinitro -phenol) is formed .

C6H3 (OH)H2

803 3HNO 21120 H,so4+ C6H2(N02)3OH,

and the ammonium salt of . p1crlc acid being yellow,this body

lends itself to quantitative colorimetric estimation .

C6H2(N02)3OH NH4OH C

6H2(N02) 3ONH4

The solutions required are:Standard potassium m

’

tm te,containing 0 -

7215 gramme KNO3 ina litre of water . One c .c . of this solution= 0

°

1 milligramme N .

A dilution of 100 c .c .

“

to a litre should be made for the anal ysis . One

c .c:will then con tain milligramme nitric N .

Phenol Sulphom'

c Acid — The phenol sulphonic acid used should

be the pure disulphonic acid which,with HNOs ,

gives, according to Kekule, picric acid even in the cold . Three

grammes pure phenol and 37 grammes c .c .) pure HzSO4 ,

specific gravity 18 4, are mixed in a beaker and heated for six hours

5 8 PRACTI CAL SAN I TARY SCIEN CE

o n a water bath at 100°C . Should the acid thus formed crys

tallize out on standing , it m ay be brought into solution by reheating

for a short time .

Process — Place I O c .c . of the water in a porcelain basin on a

water bath and in a similar basin 10 c .c . of the standard nitrate ;when just dry , add to each 1 c .c . of the phenol sulphonic acid and

allow to remain for a few minutes on the bath . Now transfer to

two N essler glasses the contents of the dishes , and wash out with25 per cent . ammonia solution the last trace of material from the

dishes ; add further ammonia to the Nesslers until all effervescenceceases and a small excess of ammonia is found in each . Spirting

may be prevented by washing out the contents of the basins into

the Nessler glasses with a small quantity of distilled water, and

adding the ammonia solution afterwards . Make up to 100 c .c . in

both cases with distilled water,and let stand for fifteen minutes .

In performing the estimation , take a third Nessler glass and

pipette into it from the more deeply - coloured cylinder (which isgenerally that containing the standard nitrate) a quantity deemednecessary to match the tint of the cylinder containing the water

sample . Make up to 100 c .c . with distill ed water, and compare thetints on a white til e . An exact match can be effected in a few trials .

Suppose that 20 c .c . from the standard solution match the water

sample , the latter contains 12

00—0o f the N as nitrates contained in

the standard . Each c .c . of the standard contains 0 01 milli

gramm e N .

10 c .c .= 0 -1 milligramm e N , but fig, of o -1 = o -oz ;

10 c .c . water under examinat ion: 0 -02 milligramme N '

100 0-2

or this water contains o °2 part nitric N per

In the case of very good waters 20, 50 or more c .c . should be

evaporated to dryness as above , and on ly 5 c .c . of the standard

nitrate taken .

The amount of sulphonic acid used ,so long as there is enough ,

is of l ittle import . In comparing the colours , the best results are

obtained when the intensity of the colour does not exceed that produced by 1 c .c . of a water containing about 0 05 part N per

The colour produced by o r part per is difficult to matchaccurately . The loss of N during evaporation is less when the

CHAPTER VI

GASES IN WATER— WATER SEDIMENT— INTERPRETATION

OF RESULTS OF CHEMICAL ANALYSES

WATER dissolves gases in quantities depending on t emperature ,pressure , and solubility of the gas . The principal gases found inpotable waters are N , 0, C02, and occasionally CH4 , H2S,

and NH3.

Of these O and CO2 are alone worthy of estimation . As organic

matter in water throughout all its stages of change lays hold of

dissolved oxygen,the presence or absence of this gas may afford

valuable inform ation regarding such organic material . These

remarks apply equally to sewage effluents .

From a hygi enic point of view the subj ect of gas extraction from

waters is not sufficientlv important to warrant the expenditure of

time arid labour inseparabl e from accurate gasometric work . Nor

is the information gained,even when the work is most exactly

performed, of constant or certain value .

Estimation of 0 Dissolved in Water (Thresh) .

When sulphuric acid is added to a mixture of KI and a nitrit e,iodine is set free . If 0 be carefully excluded, this free iodinerapidly reaches its maximum

,and remains constant . But if 0

be admitted,the amount of iodine liberat ed varies with the tim e of

exposure,and has no relation to the amount of nitrit e present .

Thresh concludes that the NO produced acts as a carri er of O,

forming N203 , which liberates more iodine and is again trans

formed into NO,and that this action continues as long as any

free dissolved O remains in the water .

2NaNO2 s SO4

ZKI K,,SO4 Na

zSO4 zHNO2 2HI .

2HI 2HNOz= I2 s O 2'

NO.

2NO O N203 .

N203 zHI ZNO I

2H20 .

I2 2Na28203 ZNaI NafiS4OG.

60

GASES I N WATER 61

In the above reactions it will be noted that free nitrous acid is

fi rst formed , and that this l iberates I .

If now the total amount of I liberated be determined, and the

FIG . 4 .

amount of I theoretically liberated by the nitrite be calculated,the

difference will represent the I liberated by the0 dissolved in thewater .

The estimation is carried out as follows (see Fig .

62 PRACTICAL SAN ITARY S CIEN CE

Into a wide-mouthed glass bottl e A , of 500 c .c . capacity , is fitted

an indiarubber cork,with four perforations . The stem of a separ

ator funnel B , holding about 300 c .c . o f the water , is pushed through

the cork . Through another perforation is run a piece of glass tube

attached by rubber tubing to the lower end of a 100 c .c . burette C,

graduated to t enths of a c .c . Through the remaining two per

forations are run pieces of glass tubing bent at right angles , one D ,

connected by rubber with a gas- tap,and the other E, by similar

tubing with a short pi ece of glass tube thrust through an india

rubber cork , which fits the top of the separator funnel . The

funnel B is filled with water to the top,and the glass stopper

inserted, displacing a small quantity of water . The contents are

accurately measured once for all , and the capacity of the funnel

noted .

The funnel is now filled with the water to be examined . The

burette C is charged with thiosulphate (1 c .c .= milligramme

made by dissolving grammes of crystalline sodium thiosulphate

in a litre of distill ed water .

[2Na2SzO3 ,5H20 12

2NaI NazS4OG.

4, 12: O .

496 16

31 1

77 5 02 5]

Having thoroughly cleaned and dried the bottle A, the cork is

inserted and the tube connected w ith the lower end of the burette C,

fixed in position . The funnel B is filled up to the top,and the

stopper inserted ; the stopper is now taken out and 1 c .c . of a solu

tion of sodium nitrite and potassium iodide (sodium nitritegramme, KI 20 grammes , distilled H20 100 c .c .) poured in from a1 c .c . pipette . From a second 1 c .c . pipette is run in I c .c . H SO4(25 per The higher specific gravity of the nitrite mixture

and of the HzSO4 solution causes these to sink rapidly to the bottom

of B , and when the stopper is replaced a negligible quantity, if any,

of the reagents just added is lost in the small amount of water

which overflows ; in this way the entry of air is excluded . The

funnel is inverted a few times , so as to effect a uniform admixture ,and its nozzle pushed through the cork . The tube D is joined upwith a gas- tap

,and gas rapidly passed through the bottl e . When

GASES I N WATER 63

all the air has been expelled the gas may be lighted at the end of E,

where it will burn quietly . The stoppe r of B is removed , and

having rapidly extinguished the flame at the end of E, the cork of

the latter“ is fixed in B,after which the tap is turned, and the mixture

of water and nitrite solutions is discharged into A . The tap of B

is now turned off, the cork at the end of E removed, and the gas

relighted and turned down to a small flame . Thiosulphate is then

run in slowly from C until the brown colour produced by the

liberated iodine is nearly removed . About 3 c .c . of a fresh starch

solution is poured into B,and 1 c .c . of this carefully run through

the tap into A,in order to definitely fix the end of the reaction .

As the blue colour returns in most instances after a few seconds , itis well to wait for a little and add a further drop or two of thio

sulphate to complete the decolori’

zation .

The amount of thiosulphate used will represent '

(I ) The -I (and accordingly its equivalent as O) liberated bythe nitrit e in the reagent

(2) The I (and its equivalent O) liberated by the nitrite , if any ,originally in the water .

(3 ) The O dissolved in the reagents .

(4) The O dissolved in the water sample .

The value of (4) can obviously be determined by subtractingthe sum .of the values and (3 ) from the total .

The values of (1 ) and (3) can be easily determined by making ablank experiment

,using five times the amounts of nitrite- iodide

solution , sulphuric acid ,and disti lled water in lieu of thiosulphate,

as it_m ay be assumed that the oxygen in distilled water is equal

to that in thiosulphate . The number of c .c . of thiosulphate solution

required div ided by 5 gives the j oint values of (1 ) and In

o rder to estimate (2) the nitrous acid in the sample must be verycarefully determined, and as 94 parts by weight of this areEquiv a

lent to 16 of O, the calculation is easily made [2HNOZFor a given piece o f apparatus

,the values of (1 ) and (3) having

been once determined,it is unnecessary to repeat the process ,

granted that the same quantiti es of reagents are always used .

In (2) the nitrous acid may be estimated by Griess’

s method .

A simpler method for the estimation of O dissolved in water isthat ofWinkler


In this method manganous hydrate serves as the oxygen carrier,

and enables it to liberate its equivalent o f iodine , which is thent itrated in the usual way .

In collecting the sample of water , care must be taken to avoid

agitating it and exposing it for any length of time to the air . It is

transferred with similar precautions by syphoning to a stoppered

bottle of known capacity— say 250 c .c . One c .c . of strongmanganous chloride solut ion (40 grammes MnC12,H20 to 100 c .c .)and 2 c .c . of a solution containing 33 per cent . KOH and I O per cent .KI are introduced by a pipette with long stern which carries itscontents to the bottom , thus displacing 3 c .c . ofwater from the top .

The bottle , which must be full of liquid ,is now closed with the

stopper without including any air - bubble , and the liquids are

mixed by several times inverting the bottle . The manganous

hydroxide precipitate which forms will be more o r l ess discoloured

by higher hydroxide , according to the proportion of O which wasdissolved in the water sample . As the oxidation of the manganous

hydroxide is not immediate, and the result is influenced by light ,the bottle is put aside in a dark cupboard for fifteen minutes ; 5 c .c .

strong HCl are added , which cause the precipitate to disappear ,and leaves the liquid coloured with dissolved iodine . The iodine

is t itrated with standard thiosulphate, of which the oxygen valueshould be known

, so as to give the amount of oxygen directly .

If 250 c .c . of water be used,it will be convenient to use a solution of

thiosulphate of 7-

75 grammes to the litre [I c .c .= milligramme

O] , as then each c .c . thus used can be read as 1 milligramme Odissolved per litre of water . It is usual , however, to determ inethe amount of thiosulphate required by the same volume of fullvaerated pure water of similar character, or of dist illed water, and thento calculate the percentage of the possible amount of oxygen presentin the poi luted water directly from the amounts of thiosulphate

which equal volumes of the two samples require . The manganous

chloride must be free from iron , and all the reagents must be free

from nitri t es .

It has been obj ected that iodometric methods are inapplicable to waters containing much organic matter, as this mayabsorb iodine— but this obj ection does not appear to be wellfounded .

GASES IN WATER 65 ,

Ordinary tap water at room temperature contains about 7 c .c . 0

dissolved per litre,or by weight about 1 part per

2MnCl2 4KOH 4KC1+ 2Mn (OH)2 .

2Mn (OH)2 HZO—l O 2Mn (OH) 3 .

2Mn (OH)3 6HC1= 2MnCl36H20 .

2MnCl3 2KI 2MnCl2 2KC1+ 12 .

CO2 in Water .

Carbon dioxide may exist in solution in water in the free state,as a bicarbonate, o r as a carbonat e .

Estimation of Total 002 (free CO2, CO2 in bicarbonates, CO2 incarbonates) — Solutions and apparatus required:BaCl

2solution , 10 per cent . HzSO4 , baryta—water, flask of capacity

about 300 c .c . , fitted with a perforated bung through which threeholes are bored

,the first carrying a funnel tube prov ided

'

with a

stopcock,to hold HzSO4 the second carrying a glass tube almost to

the bottom of the flask,.

and connected outside to a bottle containing

baryta-water ; and the third carrying a glass tube connected with a

CaCl2 tube and a . weighed’

potash bulb containing 50 per cent .

solution of KOH .

.Process .— Measure into the flask 200 c .c . of the wat er to be

examined, “and 50 c .c . baryta-water, together with 5 c . c . BaClz.

Sha ke, and allow to settle for twenty—four hours . Decant off asmuch of the clear fluid as possible without disturbing the sediment .

Should there be a scum on the surface, rapidly run the fluid through

a filter—paper, and drop the filter into the flask . Replace the bung

and run in slowly the HzSO4 , which decomposes the carbonates .

The Ba (OH)2 has previously precipitated as carbonates all the

free CO2 and that existing as bicarbonate . The total CO2 evolved

by the action of HzSO4 is absorbed by the KOH in the bulb . Weigh

the bulb ,and difference in weight represents this CO2.

When during the experiment the COZ ceases to come off, the

flask should be gently heated in order to assist the evolution,and

air drawn through in order that all the CO2 may r each the KOH .

Estimation of Free COT— Measure into a porcelain basin

100 c .c . of the water ; add a few drops of phenolphthalein ,and ru n

in from a burette a solution of st

ir Na2C03 until a faint red colour is


developed . The sodium carbonate forms with the CO2 sodiumbicarbonate (NaHCO3 ) , and immediately all the CO2 is used up

further carbonate turns the indicator red . The amount of NaQCO3

used measures the quantity of CO2 present .

I\'

a2CO3 CO2 H20= 2NaHCO3 .

106 grammes I\’a2CO3 neutralize 44 grammes CO

(g, NazCO3 contains per c .c . 0 -00265 gramme .)

1 c .c . of the sodium carbonate therefore neutralizes T4

54

6x 0-00265

gramme CO2: gramme CO2 .

If in an estimation it is found that 3 c .c . $0 NazCO3 are requiredto neutralize the CO2 in 100 c .c . water

,the amount of CO2 in this

water will be 3 x o -oo rr gramme= gramme: 3 milligrammes:

3 parts per

Estimation of Free CO2 and CO2 as Bicarbonate.— If to

100 c .c . of the water a li ttle BaCl2be added to precipitate carbonates ,

sulphates , and phosphates of any alkali es which might be present ,and which would precipitate barium from baryta-water ; and ,

further, if a little saturated ammonium chloride be added to preventthe precipitat ion of magn esia (MgCO3 would precipitate BaCO3from the CO2 existing free and as bicarbonate may be

neutralized by excess of Ba (OH)2 ; and the loss in alkalinity of the

measured excess of Ba (OH)2 solution used may be estimated bytitration with standard oxalic acid (as carri ed out in Pettenkofer

’

s

method of estimating CO2 in the air, cf. p . and converted intoterms of CO2 .

The CO2 due to bicarbonates is equal to the figure found for thisestimation less that for free COEstimation of CO2 as Carbonates and Bicarbonates.

— To

100 c .c . of the water add a few drops of phenolphthalein , which

immediately becomes red from the action of the carbonates

(phenolphthalein remains colourless in the presence of bicarbonates) .

Run in standard oxalic acid, 1 c .c .= 1 milligramme C02, until the

indicator loses colour . This measures the carbonates .

Now boil the water for fifteen minutes, and run in further standard

oxalic acid until the phenolphthalein ,which in

‘

the meantime has

become coloured,again becomes colourless .

The first addition of acid converts the carbonates into bicarbonates:hence colourless phenolphthalein .


compounds , carbonates , oxalates , etc ., is in certain cases of some

import ; but the investigation of animal and vegetable matter ismuch more l ikely to lead to positive evidence of sewage and otherorganic forms of pollution .

In this chapter a few , and only a few , general remarks will be

made on the biological examination , and the student will do well to

consult such works as Cooke’

s British Desmids ,’ ‘ Fresh-water

Algae ,’ by the same author , Whipple

’s ‘

Microscopy of Drinking

Water ,’ and other writers on the Infusoria , Rotifera , Fungi , etc .

A necessarily limited number o f illustrations are given , but it is

hoped that these will be sufficient to introduce the beginner to them iCl

‘

OSCOpiC study of water sediments , which in every examinationshould be faithfully carried out .

Much has been written on methods of procuring the sediment .

Where a centrifugal machine is at hand it is most satisfactory touse it

,and where none can be had the ordinary conical urine glass

suffices in every respect . In using the latter, the water should

stand overnight . The clear fluid is carefully syphoned or poured

away,and the sediment at the bottom is removed by a fine pipette

,

and dropped in single drops ona series ofm icrosc0pic s lides . Some

workers use well - slides . Should there be a scum on the surface of

the water in the conical glass , this is removed separately and trans

ferred in like manner to slides . Cover- glasses are applied ,and the

slides carefully examined, first by the low and afterwards by the

higher obj ect ive .

Certain biological forms inhabit only foul water, and disappearwhen it becomes purified . Where a supply usually satisfactory

develops colour,turbidity , or odour, a microscopical examination

alone may elucidate the causes . A satisfactory water should be

free from all suspended matter , and especially from all living anddead animal and vegetable matter . Certain animal and vegetable

growths may occur in storage reservoirs and cisterns through the

adm ission of light to the water:plants containing chlorophyll (greenalgae , diatoms , etc . ) grow in light . T he different seasons bear

different forms and amounts of animal and vegetable l ife, thereforea systematic microscopical examination is necessary. Vegetable

growths may take place at dead ends in mains . Much dead organic

matter will be found in the form of unrecognisable débris , but

Ui

-h

wto

i-i

FIG. 5 .

1 . Wood ce lls .

2 . Cotton fibre .

3 . Lin en fibre4 . H emp fibre .

5 . Algal zoospore .

FIG. 6 .

Fresh -water Hydra .

Scale of insect .

Egg of Taen ia so lium .

Egg of Trichocepha lus dispar .

Egg of Ascarus lumbrico ides .

6 . Particles of sand .

7 . Param oecium .

8 . Am oeba .

9 . Encysted InfusorianI O . Alga l zoo spore .

Param oecium .

7 . Am oeba .

8 . W001fibre .

9 . Eup lotes Charon .

ro . D iatom s .

r . Pleurococcus (Algae ) .2 . Am oeba (Proto zoa ) .3 . An Infusorian .

4 and 5 . D iatom s (Al gae) .6 . A Desm id (Alga ) .

Anguillula (Nematoda) .

Ulo th rix .

Zoogloea o f m icrococci .

Anab ena .

Cryptom onas .01

-tH

FIG . 7 .

7 . H a ir o f insect .

8 . Vegetab le tissue .

9 . Fibre o f woo l .

10 . Ulothrix (Algae)

FIG . 8 .

6 . Chara fragilis .

7 . D iatom (Synedra) .8 . Uroglena .

9 . A Desm id (Co smarium ) .10 . Encysted Infusorian .

FIG . 9 .

I . Vorticella . 6 . Crenothrix po lyspora .

2 . Sp i roge i ra . 7 . Vo lv ox globator .

3 . Sphaeroti lus natans‘

. 8 . Tab ellaria .

4 . Beggiatoa . 9 . Species o f N ostocfl

5 . Daphm a . I O . Me losira .

FIG . 10 .

I . Rotifer (Annulo ida) . 6 . Crystals of calcium sulphate .

2 . Param oeciurn (Protozo a) . 7 . Algal filam ents .

3 . An im al spine . 8 . N ot i dentified .

4 . Wing scale of an insect . 9 . Bacteria .

5 . Vegetab le debris . I o . Diatom .

72 PRACTICAL SAN ITAR Y SCIEN CE

amongst it much that is recognisable , as epithelium , striped muscle ,cotton , silk , and linen fibres

,starch granules , dotted vegetable ducts ,

wool , hair, o v a of intestinal worms , and numerous other bodies , all

distinctive o f sewage . It will thus be seen that a knowledge of thefauna and flora of water will enable workers to recognise certain

organisms , alive or dead , which produce odours in water, others

whi ch live only in pure waters,and whose presence excludes gross

pollution , and those which live in polluted waters , and consequently

point to sewage or other contamination . Fishy odours , according

FIG . I I .

I . Osci llatoria . 7 . A H e li ozoon .

2 . Sm all Infusorian .Egg of an. Entozoon .

3 . Free - sw immi ng Vorticella . 9 . Pith cells partia lly cov ered W i th4 . Cotton fibres .

v egetab le debris .

5 . Nav icula (Diatom ) . 10 . Wood of a Con ifer .6 . Conferv o id Alga (Synura uv ella) .

to Whipple,are produced by Endorina, Volvox , Pandorina , and

other Chlorophyceae, Uroglena , Bursaria, and other Protozoa .

Aromatic odours are created by numerous diatoms— Tabellaria ,

Meridion , Diatoma , etc . —and Protozoa . Grassy odours are‘pro

duced by Rivularia, Anabaena, Caelosphaerium , and other Cyano

phyceae.

WATER SEDIMENT 73

In river water and unfiltered supplies possessing odours the

organisms are likely to be found in the supply ; whilst in filtered

waters they mostly grow on the filters . The foul odour and reddishcolour of the Cheltenham water some years ago was shown to bedue to a species of Crenothrix growing in the reservoirs and on the

filters . In deep-well and springw aters any low forms , animal or

Vegetable , indicate insufficient protect ion from light , such as storagein uncovered reservoirs . The so - called sewage fungus , B eggiatoaalba

, including Carchesium Lachm anni , and other forms , occurs in

1 . Leptom itus lacteus (from impure 6 . H ydrodictyon (fresh -w ater Alga )r i v er) . 7 . Sand parti cles .

2 . Carchesium Lachm anni (from 8 . Alga l filam ent .

water p o lluted wi th sew age ) . H ypha o f fungus (sporing) .3 . Conferv a b

‘

ombycina (p ond w ater) . I O . Encysted Protozoon .

4 . Fre sh -water Alga (Lyngyba) . I I . Water b ear .

5 . Bursaria gastris .

effluents from sewage - farms and bacteria - beds . B eggiatoa also

occurs in river beds and stagnant waters containing HzS . Wino

gradsky holds that it does not produce the S which it contains in the

dried state, but that this S is derived from the H28 by other means .

Cohn states that it produces S fromsulphates and albuminous bodi es .The organisms forming the slimy superficial layer (Schlammdecke)

74 PRACTI CAL SAN ITARY S CIENCE

FIG. I 3 ,

— BEGG IATOA ALBA .

FIG . I 4 .

—DAPHN IA PULEX .

PRACTICAL SAN ITARY S CIEN CE

FIG . I 7 .

— LE ICESTERSH IRE W001.

FIG . I 8.

—CH IN ESE S ILK .

WATER SEDIMEN T

1 9 .

— FLAx FIBRES .

FIG . 2 0 .

— H EMP FIBRES .

7 7

PRACTI CAL SAN ITARY SCIEN CE

FIG .2 1 .

— jun“

FIBRES .

FIG . 22 .

— COTTON FIBRES .

IN TERPRETATION OF RESULTS 79

of a sand- filter are innumerable , and vary with the source of the

water and other factors .

When a sand-filter is first set to work , it acts merely as a strainer .

In the course o f a few days a slimy o rgani c layer consisting of greenand blue algae, fungi , zoogloea masses of bacteria , diatoms , and a

multitude of other organisms , makes its appearance , and true filtra

tion then commences . The source of the water , season of the year ,et c . , determine the presence of specific forms . Certain green algae

are produced in the spring , blue algae in the summer, and their

colouring matter may be liberated at any time and remain on the

surface long after the organisms have died .

The matter obtained as sediment from a centrifugal machine ,conical glass , or surface scum , when examined mic rosc0pically, may

be found to contain (1 ) l iving animal forms , (2 ) dead animal forms ,

(3) l iving vegetable forms , (4) dead vegetable forms , (5) mineraldetritus , and (6) unrecognisable débris , requiring micro - chemical and

other methods of investigation .

The differentiation of some lowly animal and vegetable o rganismsis frequently a matter of no little difficulty , but careful sear ch should

be made for these , as'

theirpresence has special significan ce .

INTERPRETATION OF RESULTS OF CHEMICAL ANALYSES.

As previously indicated, j udgment should be exercised at all t ime"

in expressing an opinion on a water without a personal inspection

of the source , etc . ; but many instances will arise in which no doubt

can exist as to the foulness o f the sample . Posit ive results in the

search for sewage contamination are much more easily dealt with

than negative . The liability to such pollution should ever be kept

before the mind of the analyst . Deep springs and wells for the

most part afford the - purest waters . Upland surface waters may be

also quit e pure . But subsoil waters and waters from cultivatedlands , as also most river waters , are rarely free from pollution .

Waters collected from the surfaces of the more impervious rocksdestitute of animal and vegetable life

,are extremely pure . These

rarely contain any appreciable NH3 ,and rarely more than 1 part

chlorine, 01 part nitric N , 5 parts hardness , and 10 parts total


solids per Waters collected from rocks covered with peatwi ll present high figures for organic ammonia , and O absorbed byorganic

‘

matter,and their acidity will be great . Such waters are

plumbo - solvent,and should be neutralized before distribut ion to

the consumer . Waters from mountain limestone are moderately

hard , with high total solids and neutral or faint alkaline reaction .

The mineral residue is chiefly composed of carbonate and sulphate

of calcium and magnesium . Great variety in composition i s found

amongst waters originating in the lias , magnesium limestone, red

sandstone, and oolite ; total solids may range from 1 0 to 15 parts ;total hardness 10 to 15 ; chlorine 1 to 2 ; and nitric N 01 to

Alluvial strata furnish waters of high total solids (50 t o 100) andwaters from cultivated soils vary within very wide l imits in total

solids , hardness , chlorine , and nitric N .

Hard waters are derived from,the chalk, l imestone, magnesian

limestone , oolite , and dolomite .

Chalk waters are mostly bright , transparent , and charged with

C02. When the COZ is driven off, these waters are almost univer

sally alkaline, although before boiling the reaction to litmus may bedistinctly acid . Chlorine varies from 2 to 3 parts , nitric nitrogen

from 02 to 04 , total hardness 15 to 30 (the hardness i s chiefly tem

porary, and may be nearly all due to carbonates of Ca) , and totalsolids from 25 to 50 parts .

Waters from oolite closely resemble those from chalk , with the

exception that they contain a little more permanent hardness .

Limestone waters contain more tota l solids and more permanenthardness (due principally -to calcium and magnesium sulphate) .

Waters from dolomite strata occupy an intermediate position between chalk and limestone waters i n point of hardnes s and totalsolids . Greensands , in that they frequently contain much nitrates

and variable quantities of ferrous iron , furnish , through the reduction

of the nitrates by the iron , quantities of free NH3. The intermediate

stage of nitrites may be occasionally demonstrated . The lower

greensand furnishes water collected at great depth— o ften many feetbelow the chalk— and accordingly the total sol ids are high , often 80to 100 parts per Hardness is very variable , and much is

permanent . Chlorine may run to 10 or 12 parts per and

nitric N to as much as 0 -

5 or 0-6. These waters are very free from

IN TERPRETATION OF RESULTS 81

organic matter . Where water is procured from lias clays muchpermanent hardness may be expected (CaSO4 and MgSO4) , 20 partsor more , and total solids may range from 200 to 300.

A water containing over 30 parts of total hardness may be con

sidered unsuitable for domestic purposes , unless it can be largely

softened .

Waters containing more than 20 parts of permanent hardness are

not suitable for washing and cooking .

Deep wells , if sufficiently steined, are for the most part pure .

Very occasionally a well in the chalk may tap a hidden reservoirof unpurified sewage which has leaked through fisSures from a cess

pool .

Sewage derives the bulk of its Cl from urine , which contains , asabove mentioned

,about 1 per cent . chlori des, but although it con

tains this large amount of Cl, it is obvious that'

deadly pollution bysewage may occur in such small

“

amounts as are wholly incapable of

detection by chemical methods ; the chlorine figure , therefore , will be

chiefly of diagnosti c value in those cases where the soil , subsoil , and

water- bearing'

strata are of constant composition and beyond the

reach of contamination by cultiv ated land . If after a series of

analyses the Cl figure is found fairly constant , a part icular rise of0 -

5 to 1 part per may j ustly arouse a suspicion of sewage

pollution .

Considering the varieties in source and surrounding conditions

from source to distribution , it is quite impossible to erect standards

of purity for waters in this country. An inspection of the sourceand surroundings is of the utmost importance in all cases .

In considering the free and saline NH3 ,the merest trace should

be considered .o i import if not suspicious , except in those Cases where

reduction of nitrates has taken place , such as occurs in the green

sands . As previously stated , if the albuminoid ammonia be very

small (less than the ‘ free and saline may be allowed to

exceed slightly 0 In peaty waters , where the albuminoid

ammonia may reach 00 1 , the free and saline should be negligible .

In a deep-well water the O absorbed from permanganate in 3 hoursat 37

°C . should not exceed 00 1 or 0 002 . In a peaty water free

from animal pollution this figure may exceed 0 -1 .

In passing j udgment on river waters , analyses , in addition to

6

82 PRA CTI CAL SAN ITARY S CIEN CE

inspect ion , should be made of all tributaries , lest evidence of presentor past pollut ion be overlooked . The search for poisonous metals

should‘

be carefully carried out, and when any of these is found aquant itat ive est imat ion should invariably be made . Lead to theextent of 00 25 part per is sufficient to condemn a potable

water . Present or recent sewage pollution may be more or lessaccurately differentiated from past and remote

,in that

,whilst

high Cl and nitrate figures obtain in both , in the present o r

recent contamination there will be marked free and organic NH3 ,

whereas in the past and remote little or no free or organic NH3

will be found . Further animal pollution may be more or less

accurately different iated from vegetable by contrast ing the twoammonias , oxygen absorbed by Tidy

’

s process , Cl , and nitrates .All these figures are high in cases of marked animal pollut ion ;whilst in vegetable pollution free NH

3is low

,organic NH

3

'

high,

Cl and nitrates are low , and in the last two no increase if thewater is drawn from below the surface . Where much vegetable

matter exists the water is usually coloured , as in the various peatywaters , and the solid residue chars on ignition . Sulphates and

phosphates occur in larger quantities in water polluted with

animal matter than in those contaminated with vegetable material .Little has been said of nitrites , because , although they are easilyform ed by oxidizing and reducing agents , they are rarely presentin natural waters . They are found in purifying sewage , but ,unfortunately

,as they may be formed from other sources than

ammonia’

(such , e .g. , as nitrates in contact with iron , zinc , and lead

pipes or cisterns) , it is not always possible to locate their origin .

The faintest trace , however , of nitrites should condemn a water,except in the single instance of a pure water containing nitrites

undergoing reduct ion by metallic or other inorganic compounds ,and not by organic matter .

The solids irnpart different properties to waters accordingto their composition

, so that no strict limit can be set to their

amount . Sulphates should not exist in larger quantity than

8 parts SOZ per Magnes ium salts , especially MgSO4 ,should be very small , i f at all present , in a good water . And per

haps , all forms ofmineral matter considered,the total figure shouldnot nearly reach 100.


tuberculosi s and acid - fast bacteria ; Neisser’

s , used for the KlebsLofller bacillus

, etc.

5 . The preparation of and results obtained by the various ferm en

tation media in common use , especially those for intestinal bacteria .

6. The methods employed in carrying out immunity reactions

between micro - organisms and blood serum .

The bacteriological examinat ion of water as a routine procedure

seeks ( I ) to measure the extent to which it has been polluted bysewage ; or (2 ) to determine the degree of completeness of purification processes ; o r (3 ) to detect the presence of definite disease

producing organisms , such as B . typhosus , etc . Sin ce the number

of definite pathogenic organisms compared with the total num ber ofbacteria in water is very small , and since competition may havewholly eliminated the disease - producers by the time the water

reaches the laboratory , the search under head (3 ) becomes so un

satisfactory that it is but rarely attempted . The search under

head (2 ) is most serviceable in determining the efficiency o f sedi

mentation and filtration of large quant ities of water . The micro

organisms characteristic o i'

sewage generally styled indicator

or’

ganisms —v iz . ,B . coli , streptococci , and B . enteritidis sporogenes

when estimated quantitatively determine with considerable accuracy

the degree of sewage pollution remaining at any stage in the puri

fication of a water - supply , and to the expert in charge this piece ofbacteriological evidence is of the first moment .

'

But the search under

head (I ) is that most widely engaged in .

B . Coli .

Of the three indicator organisms above nam ed ,B . coli is

’

by farthe most important ; so universally is this recognised that the bulkof bacteriological examinations of water is limited to a quantitative

determination of this organism alone . We have in the B . colz'

group

bacteria extremely numerous in excreta and sewage , but which do

not occur in air , soil , or water unless these have been in contact withsewage .

It is difficult to define the charact ers of the group . All its

members are non - sporing short bacilli , Gram negative, motile ,although motility is not always seen , ferm enters of glucose and

THE BACTERIOLOGY OF WATER 85

lactose with production of acid and gas , and fail to l iquify gelatinin fourteen days . Attempts have been made in recent years todifferentiate the strains of B . colz

'

found in human excreta fromthose ofthe domestic and other animals . At present it is impossible

to distinguish B . colz’

isolated from wat er as belonging to any speciesof animal . Whether or not B . coli of intestinal origin can be definitelyseparated from B . colz

'

of soil etc ., is a matter ofmuch difference of

Opinion .

"

The broad landmarks that separate the fermentationreactions of B . colz

’

from those of B . typhosus and B . enteritidis

(Gartner) necessarily disappear when variet i es of B . coZz'

are to be

distinguished . Under favourable condit ions B . coli may persist for

considerable periods outside the intestinal tract which is its naturalhabitat ; but under ordinary conditions it disappears rapidly from

soil , water , etc . This last statement is vindicated by the self

purification of rivers from“

B . coli carried into them by sewage , and

by experimentallyapplying sewage to soil , water, etc . and determ in

ing the dates at which B . colt'

can no longer be found . Whether it

be safe to rely on fine distinctions in ferrnentativ e reactions and on

pathogenic and agglutination properties as means for separat ingB . colc

'

of recent‘

intestinal origin— the type most clearly indicativeof danger— from organisms that have persisted in water, soil , etci ,after typhoid bacilli or cholera vibrios have perished, i s a question

which allk

water. investigators have to face, and until it can be

definitely answered— and that time is not yet— itwould appear to besafer to regard all forms of B . coli as possible indicators of sewage .

Houston some years ago worked out a set of tests represented by the

symbol‘

flaginac’ to assist in distinguishing B . coZz

'

of intestinalorigi n— Viz .

Greenish fluorescence in neutral red brothAcid and gas in lactose peptone mediaIndol in broth o r peptone waterAcidity and

'

clotting in litmus milk

Later he m odifi’

ed his procedure somewhat and adopted the follow

ing three tests for B . coli , using in each case portions ofwaterm easur

ing 1 00 c.c.,1

’

o c . c . ,1 c .c . , o

o1 c .c . ,0 -01 c .c .

, and 00 01 c . c .:1 . Presumptive .

—Gaseous fe‘

rm entation’

of a‘

bile salt glucosepeptone medium .

86 PRACTICAL SAN ITAR Y SCIENCE

2 . Coufirmalory.—Isolation of a coli - like microbe forming gas

ei ther in a lactose or glucose medium .

3 . Typical . —Isolation of a coli- like organism forming indol in

peptone water and gas in a lactose medium .

Houston was the first to use the above and lesser dilutions with

the obj ect of placing Public Health bacteriology on a combined

qualitat ive and quantitative basis . He used the words flaginac

and ‘ typical only as an indication that specified tests have been

carried out , and did not claim that flaginac or typical ’B . colz

‘

are only found in human excremental matter .

Techn ique of the Search for Flagiuac B . Cali — Remove bottle

of water for examination from its case and gently shake it . Removecork and flame mouth . Sow 100 c . c . of the water into 50 c .c .

MacConkey’

s fluid , triple strength , in a Durham’s tube . Sow I o c .c .

into 10 c . c . MacConkey double strength . Sow 1 c .c . into 10 c .c .

MacConkey ordinary strength . After forty- eight hours incubation

at 37°C .

‘

note presence o r absence of gas . If gas is found, dilute a

loopful o f the culture in 10 c . c . sterile water and Spread two loopsful

of the dilution on a surface culture of MacConkey’

s tauro - chloate

lactose agar for isolation . Examine after forty- eight hours for coli

like colonies . I f such he found sow one or two in a tube of liquefiedglucose - gelatin and incubate at 20° C. If gas be formed liquefy thegelatin and use it for sowing neutral red broth , peptone water , and

litmus milk . Examine for fluorescence , indol , and acid , and clot

respectively. An organism giv ing all these reactions is said to be

flaginac or typical B . colz'

.

Streptococcus Group .

There does not appear to be any uniform classification of strepto

cocci . Morp hology , pigment production ,agglutination tests , patho

genicity, and production of acid in sugars have all been recommended

as bases for classification . But for water examination attempts to

differentiate isolated streptococci have been up to the present wholly

unsuccessful .Technique of Searchfor Streptococci .

— Sow I c . c . of the water into

10 c .c . o f ordinary broth . Incubate at 37°C . After forty- eight

hours examine the deposit microscopically for streptococci .


B. Enteritidis Sporog enes (Klein) .

This bacillus possesses distinct ive characters . It is fairly large

2 to 4 M long by~o ~8

,u. broad ; it is motile ; it spores near the ends of

the rods ; it is Gram positive ; it grows anaerobicallyin milk , producinga characteristic coagulum of casein and a transparent or turbid and

acid whey,whilst gas is formed in quantity . The contents of the

incubated milk tube smell o f butyric acid . When a c .c . of thewhey containing numbers of bacilli is inj ected into the groin of a

guinea- pig the animal dies within twenty - four hours , and post

mortem.

examination reveals an extensive gangrenous slough at the

seat of inoculation . These post -mortem appearances , together

with the changes in the milk , identify the organism .

As B . enteriti dis sporogenes is a Sporing organism with prolonged

powers of resistance it can hardly be regarded as indicative of recent

excretal pollution . Indeed , Opinion is far from united concerning

its value as an indicator of sewage pollution .

Technique of Search for B . Enteritidis Sporogenes .—Sow 10 c .c . of

the water into 50 c . c . of milk , taking care to pass the pipette well

below the cream . Sow 1' c .c . into 10

'

c . c . milk . Heat the tubes to

80°

C. for fifteen minutes , and then incubate in an anaerobic appara

tus at 37°

C . The typical enteritidis change consists in formation

o fgas , odour ofbutyric acid, separation of curd, and tearing of same

by gas .

It is f impossible to set up rigid bacterial standards for waters .

But the source being known general indicat ions can readily be offered

as to what should be expected of a good water . Since the more

recent the excremental pollution the greater the number and the

O lder the pollution the less the number of B . coZi present , the bacterio

logical potentialities of a sewage—contaminated water would appear

to be best expressed in terms o f the number of B . coli found .

For deep -wells and springs a more restricted standard will bedemanded than for shallow wells , rivers , upland surface waters , etc .

For deep wells and springs it may be required that B . coli and

streptococc i be absent from 100 c . c ., and that B . enteritidis spor

ogenes be absent from a litre ; that the growth on gelatin at 22 degrees

does not exceed fifty organisms per c .c . , whilst that on agar at

37 degrees does not exceed five per c .c .

88 PRA CTICAL SAN ITAR Y SCIEN CE

In shallow wells , rivers , upland surface waters , etc . , this standard

may be relaxed to one - tenth— v iz. , absence of B . coli and strepto

cocci from 10 c . c . , and of B . enteritidis sporogenes from 100 c .c . ;

gelat in growth not to exceed 500 per c . c ., and agar not more than

50 per c .c .

Sea water is regarded as polluted by most observers when it

contains B . coli in 1 c . c . Houston states that no sam ple of sea

water remote from pollution contains B . coli or spores of Enteriti di s

sporogenes in 100 c . c . Whilst no absolute standards can be fixed it

may, perhaps , be stated in a general way that sam ples in wh i chB . coli is present in 10 c . c . , but absent in 1 c .c . , are to be regarded

as suspicious .

Technique—Collection ofSample .

— I . Awhite glass bottle , capacity

200-

500 c . c ., is st erilized and plugged with sterile cotton -wool .

2 . Before fil ling flame the mouth and remove the plug ; fill quickly ,

and insert a new cork which has j ust been passed through a flame till

slightly carbonized . Cut o ff cork level with mouth and seal with

wax . Cover with a rubber cap . In taking water from a river ,submerge bottle some distance from bank with mouth upstream ;from a tap , let run to waste before filling ; from well , lower undersame conditions as bucket is lowered, or fill from bucket , or use a

Miquel flask .

As organisms rapidly multiply in water at ordinary temperatures

the sample should be kept at 0°

C . until examination is commenced .

Special boxes containing ice are prepared for this purpose .

The label should Specify (1 ) Reasons for examination (epidemic,etc . ) (2) source of water ; (3 ) particulars concerning recent rains ,snow,

pollution , etc . purposes for which water is required (drinking,cooking , lavatories , (4) atmospheric temperature ; (5) day andhour of collection .

Enumeration ofOrganisms — Prepare a few I O c . c . pipettes plugged

at the upper end with wool, and sterilize them ; also a drop pipette

(20 drops: 1

Sterilize some coni cal flasks plugged with wool . Liquefy a fewtubes of gelat in in a water- bath , and prepare some sterile distilled

water .

Measure 9 c .c . sterile water into a flask, taking the necessary

precautions to avoid all contamination ; to this add I c .c . of the


water under investigation , and mix . The mixture is a dilution of1 in 10.

Flame the mouth o f a conical flask ; remove the plug ; introducewith the drop pipette 2 drops of the 1 in 10 dilution . Flame the

mouth of a gelatin tube , remove the plug , and quickly pour thecontents into the conical flask ; mix , and stand the flask on a cold

horizontal surface— ice in hot weather

A gelatin plate has been made containing 00 1 c . c . of the

water .

Incubate this at 20° to 22°C.

Examine the flask daily for appearance of colonies , and make

counts until the gelatin is completely liquefied .

Suppose by the '

fifth day there are 90 colonies , and on the sixth

the plate is completely liquefied , record is made that the water

contains 9,

-000 (100 x 90) aerobic micro - organisms per c .c . , liquefac

tion of the gelatin having finished the count on the sixth day .

”Enumeration may be carried out with pipettes (made in France)

which deliver about 50 drops to the c . c . The exact number of drops

per c . c . is marked on the stem .

In the same manner in'

oculate melted agar at 40°C . and pour

plates ; incubate at 37°C . for three days ; count .

Qualitative Examination — Sow 1 drop o f the water in a tube ofmelted gelatin or agar ; mix ; sow 2 ~100pfuls of the mixture into a

second tube of gelatin or agar ; mix ; sow 2 IOOpfuls of the last

mixture into a third gelatin or. agar tube ; pour plates in Petri dishes

with these mixtures . The plates are carefully observed daily , and

subcultures sown in other media for the identificat ion o f a particularcolony . Many saprophytes in water, although incapable of causinginfections , m ay, like Proteus vulgaris and M icrococcus prodigiosa s ,produce soluble toxins which inj uriously affect man and the loweranimals ; others may cause

“ a nuisance by producing in dead organic

matter foul - smelling gases .

The detect ion o f pathogenic Species , such as Baci llus typhosus , is

generally a matter of some labour . When the student has gained

facility in technique , he should conscientiously work out the various

sugar react ions , growths on special media, and the tinctorial and

morp hological characters of this and a few other pathogenic forms ,such as B . pyocyaneus , Friedlander

’

s bacillus , and the micro


organisms of suppuration . Detailed descriptions of methods mustbe sought in systematic works on pathologi cal bacteriology

Thevarious items of the analysis are recorded in some such formas this:

Sample of water fromLabelled

Brief particulars of source

Physical characters

ReactionFree and saline NH 3 parts perAlbuminoid NH ..

N itric N

Metals


Sample N o . 2 , although it possesses a high free NH3 figure , isgood . Rain water in towns is generally impure ; it i s slightly acid

from 802, and contains NH3.

Sample N o . 3 has had a small amount of untreated sewage

admitted to it .

Sample N o . 4 i s an average chalk water with low total solids .

This figure may be allowed to go up to 200 or over . The hardness

of chalk waters varies considerably .

Sample N 0. 5 .—The saline NH3 ,

chlorine , and nitrates are high ,

and nitrites are present . These items in general point to animal

NO. 5 . N o . 6.

Deep-we l l Wate r from Deep-w e l l Wa te r fromthe Lowe r Gree nsa nd . C ha lk n ea r the Sea .

Physica l char acters Good

ReactionFree and sa lin e NH3Organic NH3Cl

N itrous NNitric NH ardn ess (tota l)

(perm an ent)(temporary)

O absorb ed at 37°C . in three h ours 0 -035

Metals (Zn , Pb ,Fe , Cu) N i l

So lids (total) 260 °

5o o

(v o latil e) 35 500

(fixed ) 225-000

Appearance on ign ition Sligh t darken ingMicrosc0p ic exam ination of sedi

m ent M in era l particlesBacterio logical exam ination Exce llent

pollution ; that they are not due to this cause here is shown by thelow organic NH3

and O absorbed . Reduction o f nitrates by iron

salts is going on , as demonstrated by the high saline NH3 and

presence of nitrites .

S ample N 0. 6 is contaminated by sea water . B efore contamination Cl was 3 ,

and total hardness 20. Much MgCl2 is present , and

the water is unfit for domestic use .Sample N o . 7 contains much acid , and could not be allowed to

traverse lead pipes . Its organic NH3 and O absorbed are not sohigh as in many peaty waters.

Saline taste , gr e enish co lour , no

odour

Alka lin eN i l

o -OO3I I 5 000

N il

I -o o o

47~o o o

WATERS FROM VARIOUS SOURCES 93

N o . 7 .

Surface Wa te r, Peaty. Surface Wate r, no t Pea ty.

Physica l characters

Reaction

Free and saline NH3Organ ic NH3Nitrous NNitric NHardness (total)

(permanent)(temporary)

O ab sorbed at 3 7°C . in three hours

Metals (Zn , Pb ,Fe , Cu)

Solids (total)(v o latile )(fixed )

Appearance on ign itionMicroscopic examination of sed i

m ent N i l

Bacteriological exami nation No Intestina l or

gan ism s

Samples N os . 9 and. 10 were taken from the same house . The

analysis of 10, carried out a month after that of 9, shows some slight

variations , which are to be expected ,'

when it is remembered that

the composition of river water varies , with its varying powers of

N o . 9. N o . 10 .

New R ive r Wa te r from N ew Riv e r Wa te r fromthe Lea . the Lea .

Physical charactersReactionFree and salin e NH3Organ ic NH 3Cl

N itrous N

Nitric NH ardness (to tal)

(perm an ent)(tempo rary)

O ab sorbed at 3 7°C . in three hours

Metals (Zn , Fe ,Pb , Cu )

So lids (total)(v o lati le)(fixed )

Appearance on 1gn1tion

Micro scopic exami nation of sed i

m ent

Bacterio logica l exam ination

Co lour brown ish ; Almost co lourless ,slight taste no taste

Acid N eutra l0 °OO I o -ooz

o oo 3o o -oo 30 -600 08 00

N i l N i l

O ’O I O 0 -030

3-000 3

-000

3~oo o 2 °

5oo

N i l 0 -

500

01 50 0 -050

N i l N il

9-000 4

-000

2 ~oo o 1 -000

7-000 3

-000

Charring Fa int darken ing

Vegetab le d éb risN O intestina l or

gan ism s

Exce llent

Slightly a lkalineNi l

o -ooz

I 9 00

Ni l

0 160

205 00

I I 500

9-000

0 'O I 7N i l

32-600

I O °200

22 -

400

N il

Exce llentSligh tly a lkali ne

o 'oo r

o -o o31 08600

N il

O °Z I O

2 15 00

80 00

0 -023N i l

28-

560

1 0 -000

18-560

N i l


self-purification ,with the nature of the strata in which its Springs

of origin occur , and of the strata over which it flows , and with the

N o . 1 1 . No . 12 .

Peaty Wate r. We ll Wa te r.

Physica l charactersReacti onFree and sa lin e NH3Organ ic NH3Cl

N i trous NN i tric NH ardn ess (tota l)

(perm anent)(tempo rary)

O ab sorb ed at 37°C . i n three hours

Metals (Zn , Fe ,Pb , Cu)

So lids (total)(v o latile)(fix ed )

Appearance on ign i tionMicroscop ic exam ination of sedim entBacterio logica l exam ination

nature of the soils and subsoils of its basin , especially in regard to

cultivation , density of populat ion , and the presence of sewage and

industrial waste .

N o . I 3 . N o . 14.

Lambeth Supply. Che lsea Supply.

Physica l charactersReactionFree and saline NH3Organ ic NH3Cl

N itrous N

Nitric NH ardne ss (tota l)

(perm anent)(tempo rary)

O absorbed at 3 7°C . in three h ours

Metals (Zn , Fe ,Pb , Cu)

So lids (total)(v o latile )(fixed )

Appearance on ign itionMicroscopic exam ination of sedim en t

Bacterio logical exam ination

Co lour light- brownAcid0 0 050 -026

1 -500

N i l

o ~zzo

N i l

N i l

1 2 3 00

8 0

300

4~o oo

Charring

Vegetab le débrisN egativ e

PRACTICAL SAN ITAR Y S CIEN CE

following is an estimation:Free an d sa line NH3Total so lidsLim e

MagnesiaSi licia

H ardness

Ch lorine

The table below represents the comparative figur es for theprincipal chemical constituents of a well-filtered river water,delivered to a town of some inhabitants , and the sewage ofthe same town before treatment:

Wate r . Sewage .

Free and sa lin e NH3Organic NH30 absorb ed in two hour s at 80

°F.

Ch lorine

Nitr ic NTotal so lids

CHAPTER VII I

SEWAGE EFFLUENTS

AN average sample of the day’s working should in all cases be

obtained , and the analysis performed forthwith .

It has been usual to estimate the free and saline and albu

m inoid NH3 ,O absorbed from permanganate , total solids , solids

in solution , suspended matter, oxidized N , and C1.

The physical characters may be noted , and incubation at 37°C .

for forty- eight hours may be effected in order to determine the

presence or absence of further fermentation , as indicated by odour .

The analysis is frequently required for the determination of the

degree of purification at a particular stage , or the comparative value

of a certain method of s ewage treatment . It is usual to record the

purification as percentages of the figure for albuminoid NH3. If ,

for example,before treatment the albuminoid figure is 06 part per

and after treatment it is clear that purification has

taken place to the amount of 04 5 part per or 75 per cent .

of the original albuminoid NH3has been oxidized .

The ammonias are estimated as described underwater, but a large

dilution of the effluent is necessary ; 10 c . c . may be made up to

c . c . with dist illed water, and in some instances 5 c . c . in thesame volume will be convenient .

The O absorbed from permanganate is estimated by Tidy’s

process, and care should be taken that sufficient permanganate is

added from time to time , and that the flask is frequently shaken .

A convenient dilution is I O c . c . in a litre .

In the w‘

orking out of this process it should be noted that various

bodies besides organic matter absorb O from permanganate, suchas nitrites , sulphites , sulphides , sulpho - cyanates , numerous dves,and various coal - tar products .


Total solids are est imated by evaporating 100 c . c . o f the sample

in a plat inum dish on a water- bath . When dry , the dish is transferred to an air—bath , and dehydrat ion cont inued . It is then passedthrough a desiccator, and weighed . The difference between thisweight and that of the dish represents the total solids .

’

The solids in suspension are found by passing 100 c . c . of thesample through two folds of filter- paper , whereby the solids insolution alone pass through . The filtrate is evaporated to dryness ,further dehydrated , desiccated , and weighed . The result representsthe ‘ solids in solution .

’

The difference between this weight andthat of the total solids represents the solids in suspension .

’

In estimating nitrous N , dilute the liquid with distilled water(free from nitrite) to a convenient strength . Take 1 00 c . c . in a

Nessler glass , as described under water , add 1 c .c . metaphenylenediamine and 1 c . c . HzSO4 ( I in Match by treating in a similarmanner a standard solution of potassium nitrite made up to 100 c .c .

Stand for twenty minutes before comparing .

The nitri c N i s estimated by Crum ’s method or by the copperzinc couple . A convenient dilution must be made . Where time is

an item , as in examinations , the less accurate phenol sulphonic acidmethod may be used .

If raw sewage is to be analyzed, weaker dilutions must be used5 c .c . or less in a litre .

In the distillations carried out in Wanklyn’

s process the volume

of the boiling fluid should never be allowed to fall below 150 c .c .

Hot , ammoniafree dist illed water when necessary should be added .

Griess’

s test should be promptly performed , and if the fluid is not

transparent it should be filtered before adding the reagents .

Est imation of the total N by Kj eldahl ’s method is a much moreaccurate index of the organic pollution than that by Wanklyn

’

s

process for albuminoid ammonia . The latter usually gives lessthan half the N figure obtained by the former .

With a little pract ice Kj eldahl ’s method can be carried out rapidlyand accurately as follows:In a Kj eldahl flask put 10 c . c . sewage effluent and I c . c . H2SO4 ,

and evaporate on a water- bath to half the bulk . When cool , addabout 10 c . c . oil of vitriol , and about I O grammes sulphate o r bisulphate o f potassium (to raise the boiling -point ) . Digest under ahood in a draught - chamber . Continue the digestion unt il the solu

I OO PRACTICAL SAN ITARY S CIEN CE

the rate and degree of absorption of O are the most t rustworthy fordetermining whether o r not nuisance is likely to occur in a stream .

The fiv e days’ test represents naturally the actual pro cess by which

the more readily oxidizable const ituents o f the pollut ing matterabsorb the 0 dissolved in the riv er-water , and shows smaller differences in quality of water .

The permanganate process may give , approximately , the same

figure for a water polluted with tank liquor and for a water pollutedwith filter efli uent, while the fiv e days ’ dissolved O test will give ahigher figure for the water polluted with tank liquor , thus indicatingdifferences in kind as well as in degree o f pollution .

The Commissioners conclude that i f c . c . o f river water do

not take up more than 04 gramme dissolved O in fiv e days , the

river will be free from S igns of pollut ion ; but that i f it takes up ahigher figur e it will most probably Show signs of pollution . Thisnumber 04 thev term the limit ing figure , and regard it as the best

foundation on which to const ruct a scheme of standards .

AS results will be found to vary according to temperature , theyadopt the temperature of 65

° F . (183° and in order to provide

a wide margin of safety the dry weather flow of the river .

It wi ll be seen that the amount of dissolved O taken up in fiv edays by a mixture of river water and sewage depends— ( I ) on theamount taken up by the sewage liquor ; (2 ) on the amount takenup by the river water ; 3 ) on the proport ion in which the two liquidsare mixed .

I f x: parts of dissolved O taken up per by sewage ;y= parts of dissolved O taken up per by river wat er

above outfall ;z = dilution (proport ion of river water to sewage) ;

Thus , i f an effluent which takes up part dissolved O in fiv edays be discharged into ten times its volume of water, we get

x+ (o ~1 x 10)10 + I

SEWAGE EFFLUEN TS 10 1

— that is,in this case

,the effluent may be allowed to take up 3 4

parts dissolved O per in five days , which figure would be

the standard for this particular discharge .

The most important local condition is the degree of dilutionafforded by a river to the contaminating discharge . It is advi sed

that a standard effluent Should not contain more than 3 partssuspended solids per and that samples which satisfy thist est must also be considered in relation to the five days ’ test . The

latter is fixed at 2 parts per

An effluent which takes up 2 parts per dissolved O infive days will need some dilution i f nuisance is to be avoided . The

minimum degree of dilution required for safety can be found fromthe formula:

z = 8 .

It i s considered safe to assume that the maj ority of effluents arediluted by more than eight times their volume of river water .It i s recommended , therefore , that an effluent Should not contain

more than 3 parts suspended matter per and that , including

its suspended matter, it should not take up more than 2 parts dis

solved 0 per in five days at 183°C . It is suggested that

this be considered the normal standard for effluents . An effluent

is cons idered satisfactory that contains less than 3 parts persuSpendeds o lids , and which , after filtration , does not absorb i n parts

per more than 0 -

5 dissolved O in twenty- four hours , or

part in forty- eight hours , or 1 5 parts in five days .

Adeney’

s method o f det ermining the rate of absorption of disso lved O by polluted waters is described in detail in the Fifth Reportof the Royal Commission on Sewage Disposal .The Report (Cd . 1908) states that effluents whi ch are de

rived from strong original liquids m ay Often contain large amountsof organic matter in solution , and yet not take up dissolved oxygenrapidly from Water or cause inj ury to the streams into which theyare discharged . Such effluents , j udged by the empiri cal t estshitherto in common use , might be regarded as polluting liqui ds .The effect of an effluent on a stream does not depend on the absoluteamount of organic matter in it , but on the nature and condition of


that organic matter, and the important thing to ascertain is theextent to which the original organic matter has undergone fermentat ion . Dunbar has shown that after a certain percentage purificat ionthe residual organic matter in certain sewages is so altered as tobe non - putrescible .

To determine the rate of absorption o f dissolved O , it is on ly

necessary to ascertain by a volumetric pro cess the amount o f dissolv ed O in the effluent when fresh , and in a port ion o f the sameeffluen t aft er it has been kept for a definite period of t ime— two tofive day s . The di fference between the two estimat ions will givethe amoun t of O absorbed during the time o f keeping , and the rateo f absorption may be taken to be uniform , at least for the first twodays o f observat ion .

If a knowledge of the attendant changes which take place duringthe various stages of the fermentation be required

,it will be neces

sary , in addit ion to est imation of the dissolved O , to determine theNH

3 and HNO2 and HNO3 before , during , and after period o ffermentat ion .

For most pract ical purposes it is only necessary to determinethe rate and total absorpt ion o f oxygen and the character of thefermentat ion , whether a carbon or nitrogen one . The first can bedone by est imat ing the loss of O in the atmosphere of the flask con

taining the polluted water , and the second by ascertaining whethenitrites and nitrates have been formed or not . In most cases , however, as Adeney shows , even this will be found unnecessary , as the

complet ion of the carbon - oxidation stage of fermentat ion will beindicated by the cessation of the absorpt ion of oxygen which occursduring

'

the interval of rest which takes place before the commencem ent of the nitrogen - oxidation stage .

The Process — A measured quant ity of the polluted water (100250 c . c .

, according to amount of pollut ing matters contained) isdecanted into B , into which a little freshly precipitated magnesiumhydrate has been previously placed for the purpose of fixing the

CO2 in the water . A similar volume of dist illed water is poured intoA . Similar volumes of air are thus left in the two bott les . Thesevolumes should be sufficiently large (capacity ,

a litre or more ) toensure much more O in B than can possibly be used .

Corks , connecting - tube , and stopcocks are fitted . A Slight rise of


cautiously allowed to flow into B the water in the connecting - tubew i ll gradually S ink back to the index , at which instant the stopcockto B is closed . The reading on the burette is equal to the volume of

O , which has been absorbed from the atmosphere of B at the temperature and pressure obtaining at the commencement of the experiment.

The dist illed water bottle A acts as a reference pressure bottle .

If a comparatively rapid absorp tion of O occurs during the first houro r two and this is followed by a S lower and regular absorpt ion , it

may safely be taken to be due to the pollutedwater being de - aerated

to start with , and possibly also to the presence of easily and directly

oxidizable substances in it ; the subsequent S lower and regular

absorp tion being due to indirect oxidation accompanying the fermentat ion of the polluting matters .

It is very important , as noted above , that sufficient excess of airbe always secured , otherwise the Operation is open to certain obviousinaccuracies . The replacement of the absorbed O by water isequivalent to increasing the pressure of the N in B , which will lead

to absorp tion of N by the polluted water and the distilled wateradded to it , unless the air in the bottle be in such large excess thatthe O absorbed be only a small fraction of it . Further , with insuffi cient air there may be such a reduction in the store of O in theatmosphere of B as to lead to appreciable reduction in the rate offerm entation in the polluted water .

Bacteriological Examination of S ewage and Sewage EfiuentsHouston ’s method of water examinat ion is equally suitable forsewage effluents and sewage when these have been properly diluted .

In the estimation of B . coli it may be necessary to work on as small

a quantity as 00 00001 or even 0 -00000001 c .c . of sewage .

CHAPTER IX

Analysis of Soils.

THE analysis of soils is a large subj ect , and requires for its proper

execution a special training in chemistry . For public health pur

poses , how‘

ever,‘ very few estimations are required, and these are

of a simple kind . The powers which a soil possesses for absorbing

and retaining moisture are of some importance , but direct examination of the soi l and subsoi l in position in a given locality

'

will

furnish more valuable information than laboratory tests .

The capacity for absorbing moisture may be estimated by means

of a percolator and burette . A quantity of dried soil (say 100

grammes) is flooded with‘

water for two hours and allowed to drain for

four hours . The difference in the reading of the burette before andafter the Operation gives the number of c . c . o f water absorbed by

100 grammes , or the absorption per cent .Perhaps a simpler method is the following:One hundred grammes of dri ed soil are covered with water in acylinder . Sufficient time is allowed for saturation , which in the

case of clay soils may be several hours . The water is drained off

through a muslin filter,and the soi l is reweighed . The increase in

weight roughly represents the percentage absorption .

The determination of the size of the particles of a soil is carriedout by using a series of sieves possessing meshes . of 2 millimetres

,

I millimetre, and 0 -

5 millimetre respectively . A number of meshes

larger than 2 millimetres may be used .

One hundred grammes ofdri ed soil are pulverized with the fingers .

The larger pebbles , roots , etc .,are removed and weighed . The residue

is transferred to the 2 -m illirnetre sieve ,'

and when all has passed

that will, the remainder is further rubbed between the fingers , and105


once. more Shaken on the siev e . What remains on this sieve isweighed . In like manner the amounts left on the other sieves areweighed . Finally , the soil which passes the 5 -millimetre sieve

is weighed , and the results are collected as (a ) coarse masses removedbv hand . (b) masses kept back by the 2 -millimetre sieve , (c) sandretained by the I -millimetre sieve , (d) fine sand retained by the

-millimetre sieve,and (e) fine soil passing the 0-

5-millimetre sieve .

The specific heat of soils is determined by a sens it ive calorimeter .

The specific heat ranges from 0 -2 to 05 ,and is greatest in peaty

soils .

The determination of the porosity of a soil is effected by finding

the real and apparent specific gravity of the soil , and dividing the

latter by the former .The real Specific gravity is obtained by placing in a 50 c . c . Specific

grav ity bo tt le 10 grammes of the soil dried at 1000 C . to constantweight , rinsing the last particles into the bottle with dist illed water ,and making up with dist illed water to the mark . The whole isw eighed at 15

°C . The weight o f the water displaced by the 1 0

grammes of soi l is thus easily calculated . The weight of the soilv iz .

, I O grammes— divided by the weight of displaced water is theSpecific gravity .

The apparent Specific gravity is obtained by filling a c . c .

cylinder with soil , introduced in small quant ities at a time , andthoroughly sett led in the cylinder by tapp ing from t ime to timeon the bench . When full the cylinder is covered with a glass plateand weighed . The weight of the soil (cylinder full cylinder empty)divided by is the apparent Specific gravity .

The real specific gravity o f a sample was found to be and1 -

36the apparent the porosity is therefore2 -

46” 0 55 , or expressed

as a percentage = 55 per cent .

Pore volume , or porosity , being the sum total of the interst itialspaces which may be filled with water o r air , or both , does not depend

011 the s ize of the part icles but on their uniformity ,or want of

uniformity , of size , and on their arrangement . The porosity of asoil composed of uniform spherical particles the size of peas is thesame as that of another composed of part icles the size o f small

shot , and in each case is about one - third of the whole .


Oxidize over a flame at a low red heat , transfer to desiccator , and.weigh . The loss in weight gives roughly the amount of organicmatter .

Lime may be est im ated thus:Dissolve a few grammes of the driedsoil in dilute HCl, and dilute the result ing solut ion to about 100 c . c .

with water . Heat , add NH4OH in slight excess , and a solut ion of

ammonium oxalate also in slight excess . Allow the precipitateto settle in a warm place . Pass the clear liquid through a smallfilter and then bring the precipitate upon it . Wash with hot

water and set the filtrate and washings aside . Push the precipi

tate and filter - paper through the funnel into a flask , add

some HZSO4 , dilute freely , warm to 60° or and run in per

manganate unt il faint pink remains . Each c . c . of{if permanganaterepresents gramme CaO.

Magnesia.— Evaporate the filtrate and washings to small bulk on

the water - bath , render alkaline with NH4OH , add sodium phosphate ,and set aside for eight or ten hours in order that the magnesia mayseparate out as NH

4MgPO4 ,6HZO. Wash this precipitate on toa filter with ammonia solution . Dry in hot - air chamber and igniteto form Mg2P2O7 , from which the weight of MgO is easily calculated .

Or the ammonio -magnesium phosphate precipitate may be broughtupon a filter washed with ammoniacal water in the cold, dissolvedin acetic acid , and t itrated with standard uranium solution , each

c . c . of which represents gramme magnesia .

The phosphoric acid in soils is determined as follows:( I ) Incinerat eand digest a weighed quant ity of the soil with HCl, evaporate todryness to render silica insoluble , redigest with acid, filter, and wash .

(2) C oncentrate the filtrate and washings to small bulk and addexcess of ammonium molybdate in nitric acid , stand aside in a warmplace for two days , decant the liquid through a filter , wash the precipitate several times by decantation first with dilute HNOa, and

afterwards with small amounts of disti lled water , then transfer itto the filter and wash free from excess o f acid , dissolve the am

m on ium - phospho -molybdate in ammonia , add magnesium mixture ,filter , wash , dry, and ignite the precipitate. Weigh the resultingMg2P2O7 , from which calculat e the P2O5 .

Or the method described for magnesia may be used , wherein theammonio -magnesium phosphate precipitate is dissolved in aceti c

SOIL 109

acid,and titrated with standard uranium acetate or nitrate solution,

each c .c . ofwhich equals 0 -005 gramme P205 .

The total organic nitrogen of soi l is best estimated by Kj eldahl’

smethod . The ammonia resulting from the dist illation of the am

monium sulphate with excess of KOH is received in {if or ar

tHzSO4 .

At the end ofthe distillation the standardHzSO4 remaining is titratedwith standard alkal i , and the ammonia absorbed by the acid caleulated . The N forms {é by weight o f the NH3

.

Where total N (includingHNO2 andHNO3 ) is required the oxidized

N must first be converted into NH3by boiling with Al and NaOH,

or by the action of the Cu-Zn couple .

Clay and humus are the two most important ingredients o f soils .The plasticity and adhesiveness o f clay, together with the fineness

of the particles , serve to hold together various other aggregates of

soil . The extreme fineness of the part icles of clay causes it to retainwater , solids dissolved in water , and gases .

If by plastic or colloidal clay be understood the particles of soil

under 00 1 millimetre diameter which remain suspended in a columnofwater eight inches high for twenty- four hours , soils may be div ided

in to the following six classes:Very sandy soils containing up to 3 per cent . clay .

Sandy 3- 10

Sandy loams 10- 15Clay I 5

—25Clay soils 25

-

35Heavy clays 35

-

45 and over .

Admixture of fine powders , such as Ca (OH) 2 and Fe2(OH) 6diminish greatly the adhesiveness of clay

,caused by the hydrated

si licates .

Humus or vegetable mould is formed by the decomposition

of organic matter, largely cellulose , derived from the roots , stems,and leaves of plants . Its accumulation near the surface is natural

,

and it distinguishes soil from subsoil . Its product ion is controlledby moisture , oxygen , temperature , and micro—organisms . With a

low temperature and as much water as will shut out air the organisms

that transform vegetable tissue into humus are bacteria ; but thedisinfectant co‘mpounds produced soon kill the bacteria , and theprocess remains henceforth a slow and purely chemical one . In

1 10 PRACTICAL SAN ITAR Y S CIEN CE

the solid brown decomposit ion products formed in peat are foundulmic and apocrenic acids soluble in caust ic and carbonated alkalies ,and for ming insoluble salts with the earths and metals , and ulmin ,

insoluble in alkal ies but afterwards soluble on oxidat ion . CO, and

CH4 are formed in large quant it i es under these condit ions . Pro

longed cult ivat ion of soils t ends to product ion of acids ; hence theadvantages o f calcareous format ions . In the presence of earthycarbonate , especially that o f l ime , which neutralizes acids as formed ,

moderate degr‘ees o fmoisture , and free circul‘ation of air , hum ificationproceeds under the influence o fmoulds inst ead of bacteria . O andH are eliminated as CO2 and H O , and an increase takes place in thepercentage of C and N . When hum ification is complete andoxidat ion proceeds , the N may rise to high figures , port ions beingwholly oxidized to nit rates .

Humus is highly porous , absorbs wat er and gases , and is graduallyoxidized by bacteria . The measure of this oxidat ion can be gaugedbv the amount of CO2 produced . Humus substances are gelatinouswhen moist , but not markedly adhesive or plast i c . The density of

humus is about 1 -

4 ; hence soils rich in humus are light (humus is thelightest ingredient of soil) when compared with clay and sandysoils , and light in the agricultural sense of being easily tilled .

The N of humus does not exist in the form ofNH3 ,as it cannot be

set free by treatment in the cold with lime or alkalies . When humusis boiled with lime or alkali es ammonia is slowly evolved for an

indefinite t ime , but the whole of the N is not expelled . Such be

hav iour , together with its slightly acid reaction , points to hum usbeing of the nature of an amide - compound .

Humus formed from sugar, cellulose, gums , etc . , combines withammonia as with other bases , and at first the ammonia can be readilyexpelled from this as from other ammonia salts . But after a t imethe amidic condit ion appears to be assum ed , as caust ic alkalies actbut slowly , and are unable to expel the whole of the N . These factsare of importance in nature , as NH3 , generated in or taken up by thesoil , is in the course of t ime rendered inert and unavailable for plantsunt il nitrifi cat ion has been effect ed .

Humin and ulmin found in the deeper layers of peat are in processof t ime oxidized into humic and ulmic acids capable of combiningwith bases . Further oxidat ion produces crenic and apocrenic

1 1 2 PRACTICAL SAN ITAR Y S CIEN CE

tion of ammonium salts . Common examples of soil organisms ofthis type are—Baci llus mycoides , B . subtilis , B . mesentericus vulgatus,

Proteus pulgaris , P . zen/eeri , B aci llus coli , B . putrificus , B . lactis aero

genes , B . fluorescens liquefaciens , streptococci , etc . In acid soilsrich in humus certain fungi such as Penicilliurn glaucum, Mucormucedo

,and species o f Botrytis and Torula accomplish the cleavage

of proteins .

N itrification is carried out in two stages:ammonium compoundsare oxidized to nitrites by such organisms as Winogradsky included

in the genus Nitrosomonas europaea and nitrites are oxidized to

nitrates by several forms included in the genus N itrobacter . The

condit ions necessary to these changes are definite . In addition tonitrifiable material and nitrifying bacteria , a fairly high tempera

ture (24° a moderate degree ofmoisture , free access of oxygen ,

a base or its carbonate with which the acids formed in the processof oxidation can unite , free COZ, and darkness are essential . In

acid soils nitrification ceases , as also in soils in which the bases have

become fully saturated . Carbonates of lime and magnesia are the

bases most favourable to nitrificat ion , and excess of these producesno injury . The amounts of carbonates of potash and soda must be

strictly limited . The nitrifying organisms are strictly aerobic ; in

non - porous or water- logged soils they quickly die out . They derive

their carbon from CO2, as when cultivated in the presence of

carbonates in an atmosphere washed with KOH they fail todevelop .

Various denitrifying bacteria have recently been studied . Oneof the most effective organisms is Burri

’s B . denitrificans , found on

the surface of o ld straw and in fresh horse - dung . I f some fresh

horse - dung be placed in a close -flask containing KNO3 , nitrogen

and carbon dioxide are evolved , and in a few days the nitrate hasdisappeared . B . butyricus , which in the absence of easily reduciblecompounds evolves free nitrogen , reduces nitrates to nitrites , and

also forms NH3by addition of H to N j ust set free by reduction .

B . mycoides forms ammonia from antecedent proteins , and also

reduces nitrates to nitrites and ammonia . Reduction may be to

nitrites , and no further ; it may go on to ammonia ; nitrates andnitrites may be reduced with evolution ofNO and N20 and , finally ,nitrates and nitrites may be reduced with production of free N . A

SOIL 1 13

large number of bacteria found in faecal matter, water , and soildecompose nitrates w ith evolut ion of free N .

The reactions between nitrates undergoing den itriflcation and

organic carbon compounds may be represented by the equations:

C 2NaN03= CO

22NaNO2

C + 2NaNOz= N20 NazC03C 2N20= 2N2 C02,

where C represents the oxidizable carbon of the carbon compounds .

An important group of soi l bacteria is found in connection withthe root nodules of leguminous plants .

The mode of supply of nitrogen to plants was long a subj ect o f

debate . Liebig thought that it was derived from the ammonia inrain water . B oussingault proved that plants do not take N directly

from the air . Lawes and Gilbert confirmed Boussingault’s conelusions . Hellriegel and Wilfarth pointed out that the tubercleson the roots of leguminous plants are produced by bacilli whi ch

absorb free N from the air , and pass it over to the host . B eyerinck

later separated and described the B . radicicola .

The tissues o f one of these nodules on m icrosc0pic examination

are found to contain a number of free motile bacteria, and a num berof quiescent forms .much larger in S ize . When the nodul e hasreached full size , the large quiescent bacteria begin to collapse, and

part with their nitrogenous substance . Later the shells drop off

and carry minute bacteria into the soil , which in due course againbecome active . The nodules adhere but loosely to the roots . The

ease with which they may fall off doubtless accounts for the difficulty experienced in transplanting l egumes .

The nodules above mentioned vary in shape and size, accordingto the species of leguminous plant to which they are attached, andare caused by the Baci llus or Pseudomonas radicicola (Beyerinck)penetrating the root hairs . On entering root hairs the organismdevelops and forms a thread- like zooglea techn ically known as the

infection thread,’ which resembles the hypha of a fungus , and which

excites the neighbouring cells of the rootlet to rapid mul tiplication

and the formation of the nodul e . In the infection threads andyoungest nodules the organisms are straight rods . In older parts

they are branched and curved, and are known as bacteroids which

8

1 1 4 PRACTICAL SAN ITAR Y S CIEN CE

have lost their power of division:later they are digested by a proteoly~t ic enzyme secreted by the protoplasm of the root . The digested

substances pass to the flowers and seed s of the ripening plant . N

fixation reaches a maximum at the time when the plants begin toflower . When the crop is harvested , a large surplus . of nitrogen is

left behind in the nodules in the soil .Other bacteria are known to absorb free N , of which may be

ment ioned Winogradski’

s Clostridium pastorianum and Beyerinck’

s

Azotobacter .

The nitrogen - fixing powers of soil may be determined by esti

mat ing the total N in , say , 200 grammes o f soi l , and repeating the

experiment after six weeks ’ incubation at 20°C . in a solut ion

composed of grape sugar 40 grammes , K2HPO4 2 grammes, NaCl

2 grammes , CaCO3 10 grammes , and water 2 l itres .

The nitri fying and denitrifying powers of soils can be estimated

in the same manner by adding known quantiti es of ammonium salts ,nitrit es , and nitrates , respectively, to a suitable inorganic medium

containing a soluble carbohydrate .

When the surface soil is wetted , moisture may rise toward the

surface from the lower layers ; this is probably due to evaporation

from below, followed by recondensation by the cool wetted layer .

The condition is of some practical interest , inasmuch as cold rain

on the surface may raise water from below .

The downward percolation of water is most rapid in those soils

in which capill ary ascent is quickest in coarse sand .

The rapidity of percolation decreases as the wetted soil column

increases in depth ; as the wetted column lengthens , the frictional

resistance increasingly Opposes the effects of the hydrostatic pressure

from above until downward movement becomes little more than

lateral movement o r capillary ascent from below. The fri ctional

resistance has counteracted gravity to such a degree that the capillary coefficients o f the soil become the governing factors of thewater movement .

It is Often desirable to protect a soil from excessive evaporationin order either to prevent lowering of temperature or to save vegeta

t ion in time of drought . The preparat ion by ti lth of a layer of loosedry surface soil i s the best means of securing this obj ect . It would

appear on first sight that such a soil admits of ready access of air ,


to rheum atism and diseases of the respiratory tract . Lowering ofthe ground-water level by drainage has largely improved the healthconditions o f many soils . Soil dampness appears to be connected

with pulmonary tube rculosis .Typhoid fever , cholera , dysenteries , and other intestinal maladies

hav e been et iologically related by various observ ers to soil , groundair, and ground-water:it is probable that each and all of these actas media of conveyance o f the specific micro - organisms of these

diseases .

NewsholIne regards epidemics of diphtheria as intimately related

to dry years , and holds that they do not occur when the rainfall i s

above the average .

Malaria is connected with soil conditions in the breeding of the

Specific mosquitoes .Ankylostomiasis or uncinariasis is intimately connected with the

soil , in that the eggs of the parasite Ankylostomum duodenale escape

with the faeces and are deposited in the soi l, where they hatch intwenty - four hours . The embryos shed thei r skin twi ce , and after

a few weeks are ready to infest man . The chief portal of infect ioni s the mouth . Several observers assert that the parasites can reach

the intest ine through the skin .

The various theories which connected goitre with particular con

stituents of the soil, such as metallic sulphides , magnesian limestone,etc .

, are now practically abandoned.

Bacteriolog ical Examination of Soil. —This examination is of

service principally in connection with water- suppli es ,more especially

contamination ofwater by surface washings . Much work has been

done on B . typhosus in soi ls, and findings have been very varied .

Under favourable conditions it appears that thi s organism cansurv ive for a considerable time.

The organisms of tetanus and malignant oedema are widely dis

tributed in cultivated soil . They are isolated anaerobi cally fromsmall quantities of soi l or soil washings in the usual way. Advan

tage is taken of the fact that their spores surv ive heating at 80° C.

for a quarter of an hour, when all non - sporing organisms are destroyed . These spores are grown on various media over alkalinepyrogallic solution , and the fgrowths investigated in the usualmanner .

SOIL 1 1 7

In collecting soil for examination , the depth from which thematerial is to be recovered havi ng been decided upon , a sterile instru

ment is used for procuring six to twelve specimens , which are mixedin order to produce an ave rage sample . This is carried to the

laboratory in a sterile vessel .

A gramme is Shaken up in 100 c .c . sterile water in a sterile flask ,and from this dilutions are made— 1 c . c . of this solution is trans

ferred to 100 c .c . steril‘

e water in a second flask , etc .

Q uantitative and qualitative estimations of B . coli , streptococci ,and B . enteritidi s sporogenes are carried out in these liquid preparations in the same manner as i n dealing with water .B . coli is absent from un contaminated soils, or present in very

small numbers only . Houston finds that it is not readily isolated

even from polluted soils unless the contamination is recent andlarge in amount . He considers the spores ofB . enteritidi s sporogenesindicative of contamination, but not necessarily recent . Strepto

cocci are found in minimum quantities of soil recently polluted withsewage . They d isappear extremely rapidly.

CHAPTER X

THE air is am echanical mixture of gases . One hundred volumescontain , roughly, 21 of oxygen , 78 of nitrogen , and 1 of argon ,krypton , helium , neon , zeon, and carbon dioxide .A distinguishing property ofgases is that a mass of gas introduced

into a closed vessel always completely fills the vessel“

,however large .

Consider two vessels of equal volume connected by a tube carrying

a tap , and let one of these vessels be filled with a gas and the otherexhausted , on opening the tap , the gas rushes into the exhausted

vessel unti l the same quantity of gas exists in each vessel . Close

the tap , and once more exhaust one of the vessels ; on Opening the

tap, the gas expands and again fills equally the two vessels . The

Operation may be repeated indefinitely , and the gas will always

exert some pressure on the inside of the containing vessel .The density of a gas , l ike the density of any other body , is the

mass of unit volume , and is sometimes referred to hydrogen and

sometimes to air as unity at 0° C., and under a pressure of one

standard atmosphere .

The onl y elasticity ofwhich a gas is capable is that of volume orbulk , since it i s alone to a change of volum e that a gas offers anypermanent resistance .

I f the pressure on volume V of a gas be increased from P to P p,

and as a consequence the volume be reduced from V to V—v , the

temperature remaining constant , then the strain produced in

volum e V is v , and per unit volum e and the corresponding stress

p. Therefore , since the elasticity of a body is the ratio of the

s t ress to the strain , the elasticity of the gas is p: pg.

By compressing air with mercury in a U- tube closed at one end ,1 18

1 20 PRACTICAL SAN ITAR Y SCIEN CE

At any other temperature T , i f when the volume is constant thepressure is 15

1, and when the pressure is constant the volum e is v 1

or the pressure at constant volum e varies direct ly as the absolutetemperature , and the volume at constant pressure varies directly

as the absolute temperature .

A Barometer i s an instrum ent used for measuring the pressure

exerted by the atmosphere . Barometers may be div ided into twoclasses:(1 ) Those in whi ch the pressure is measured in terms of theheight of a column of a liquid ; (2) aneroid barometers , in which thepressure is measured by the strain produced in the lid of a metal box .

Mercury is practically always used in liquid barometers on account

of its great density rendering the height o f the colum n supported

by the atmosphere a convenient quantity with whi ch to work .

Further ,mercury does not , as does glycerin , absorb moisture from theair ; it has a fairly low freezing

- point , and a high boilingpoint .

The S implest form of barometer is the S iphon barometer , consisting

of a U- tube, the longer limb (86 centimetres) ofwhich is closed whilethe shorter is Open . The tube is filled with mercury ; by boiling the

mercury any air or moisture adhering to the mercury or bore of thetube is expelled . The distance between the levels of the mercury in

the two limbs is the barometric height . When the pressure increases, the mercury falls in the Open limb and rises in the closed by

the same amount,so that the di fference of level i s double the rise in

the closed end or fall in the Open . I f a scale be attached to eithertube

,and each inch or centimetre, as the case may be, be marked

half an inch or centimetre , the reading at once gives the height of the

barometer .In the Fortin barometer the scale is graduated in inches to 00 5 ,

and the vernier usually reads to 00 02 inch . The cistern is closed

below by a leather bag protected by a metal Sheath, into the bottom

of which is fitted a screw for the requisite adj ustments . Having

Al l? 12 1

taken the temperature by the attached thermometer, the mercury

in the cistern is raised or lowered by the screw until the ivory point(fiducial point ) or zerO . Of the scale and its reflected image in themercury are just in contact ; the vernier is then moved by the uppermilled head until its lower edge j ust excludes the light from the topOf the mercurial column ; the reading is

then made fromthe scale and vernier .Verniers are of different lengths , andcontain variable numbers Of divisions . A

common form is 1 inches long, divided

into twenty-fiv e parts , which correspond

in length with twenty- four divisions of

the principal scale .

’

A division on the principal scale is there

fore greater than one on the v ernier by

x 1% inches) (71-5 x 1 inches)25 24600

00 02 inch .

x I'

2 inches

TO read the vernier adj ust its lower edge

with the top of the meniscus , when two

very small triangles Of light will lappear,one on either side . If the lower edge of

the vernier correspond with a division of

the principal scale, this IS the reading ;but if not

,it is evident that the interval

between the surface-

of the m ercurylandthe division ‘ Of the 2 principal scale nextbelow is equal to thei

'

difference between

the lengths of the divisions of the vernier FIG . 2 4 .

and principal scales (O-Ooz inch) multiplied

by the number of vernier divisions which intervene between the

lO'

WGi‘ edge (zero of vernier) and that division which ‘ exactly corre

Sponds w ith a division on the principal scale .

Suppose in a given example that the lower edge Of the verni er

cuts the principal scale between 29 15 and 292 inches, and when the

vernier scale is examined it is found that its thirteenth div ision


corresponds w ith a division o f the principal scale , the readingwill be:

29-15 inches 13 x o o oz inchesinches + O~026 inch

29-r76 inches .

The Kew barometer, originally invented by Adie for use at sea,has a closed iron cistern , and scale of contracted inches . The tubeis of small calibre throughout , in order to lessen the oscillations of themercury by the ship ’s motion (known as pumping A smal l

aperture , covered with leather, i n the roof Of the cistern , allows

atmospheric pressure to exert itself on the contained mercury.

Fitzroy’

s gun barometer is a modification O f the Kew .

Hooke’

s wheel barometer is a siphon barometer . On the surfaceofthe mercury in the lower limb is a float carrying a needle indicator,which moves on a graduated circular dial .

Various self- recording barographs are on the market , records

being obtained mechani cally , photographi cally , and electri cally .

In order to make an Observation of the barometer comparable

with other Observat ions taken at other times and places , certaincorrections must be appli ed to it ; some Of these refer to an individual

instrument , and others to all readings of any instrument . Of theformer class there are three— corrections for index error , capacity,and capillarity . Of the latter class there are also three— correctionsfor temperature , altitude , and gravity .

The index error ismade by the workman who laid Off the scale ofthe instrument . It is discovered when the instrument is verified at

Kew or elsewhere . Correction for capacity depends on the propor

tion borne by the sectional area of the tube to that of the cistern .

At one point of the scale the reading i s correct ; when the mercury isabove that point the correction is additive , when below subtractive .

Capillarity between glass and mercury tends to depress themercury , and in larger degree the smaller the tube ; i t is also greater

in an unboiled ’ than in a boiled ’ tube . All certificates from

Kew for Kew pattern barometers give a correction at each 5 inch,i ncluding the above three correct ions .Corrections independent of the Special Instrument. -Tem

perature .— If the scale by means of whi ch the height of the column IS

measured be correct at 0° C . , then at all temperatures above O° the

length of the divisions will be too great , since all metals increase in


If H0 be the height under standard conditions corresponding to

the same pressure as does H at the place of Observation ,

Hg:Hog“; or Ho 2

1gcos

45

21—0 -oooooozf) .

I f a bubble of air be passed into the vacuum of a barometer , themercury falls ; i f several bubbles be passed in , each produces a de

pression . I f instead Of air a drop of ether be introduced , the

mercury also falls and the ether becomes completely vaporized ,even

at a temperature much below its ordinary boilingpoint . I f suc

cessiv e drops of ether be introduced , it will be found after a time that

fmther addition of ether fails to produce further depression , andthat the ether does not vaporize , but floats on the top of the mercury.

Now , i f the space above the mercury be enlarged or diminished by

raising o r lowering the barometer- tube in the cistern , i t will be found

that so long as any liquid ether remains , the height Of the mercurycolumn is constant , but that the amount of ether whi ch vaporizesvaries with the space above the mercury . I f the temperature be

increased,more ether vaporizes , and the mercury column becomes

more depressed . The vapour exerts a pressure which partly balances

the pressure of the atmosphere . The depression Of the mercurymeasures this vapour pressure . When excess of liquid is present , so

that the vapour exerts its maximum pressure , the vapour is said tobe saturated . If , on the other hand , more liquid would vaporize onintroduction to the vacuum the vapour is said to be unsaturated orsuperheated . The vapour pressure , or tension of a liquid , depends ontemperature only . Non - saturated vapours obey Boyle ’s and

Charles’s laws only approximately , approximation being the more

complete the further the vapour is removed from its saturation

point .

Altitudes are calculated from barometric readings either ( I ) byLaplace ’s formul a , o r (2) by Apjohn

’

s formula .

Laplace ’s formula iszt t

’

)D= (108 P— log p) ( Iwhere D= di fference in altitude in metres of the two stations .

P= barometric pressure in mm . Hg at Power station .

1) highertemperature in °

C . at lower station .t

t’

higher

A IR 125

Apjohn’

s formula is

(P p) 2t+ t’

DP + p

x

where D= difference in altitude in metres Of the two stations .

P= barometric pressure in mm . Hg at lower station .

fi nhlgher

t temperature in °C . at lower station .

t’ higher

Thermometers — The freezing- point of a thermometer is deter

mined by surrounding the bulb with a mixture Of i ce and distilled

water . The boilingpoint is fixed by suspending the instrument in

steam issuing from water boiling at a pressure of 760 mm . Of Hg .

The tube is then calibrated between these two points into 100° in the

Centigrade instrument .

Errors_

of M ercury Thermometers —T he Observed expansion is

really the difference between the expansion Of the mercury and ofthe glass surrounding the mercury . As different kinds Of glass do

not expand exactly alike , thermometers made of different glasses donot completely agree . Owing to the gradual recovery of the glassfrom the effects of the heating to which it was subj ected when thethermometer was made , the zero - point rises , at first rapidly, later

slowly .

One of the Oldest forms of self- registering thermometers providedwith a Contrivance to mark the highest or lowest temperature Obtaining m a given interval Of time, is that Of Six, made in the

eighteenth century . It consists Of a glass tube bent twice at rightangles , and furnished with a bulb at each end . The bulbs are fil led

with spirit , except that a bubble of air is placed in the smaller one .

The bends Of the tube are occupied by a column of mercury . TWO

steel pins sealed in glass tubes have hairs attached to them,so that

theymay retain any position reached by being pushed by the mercury

column . A magnet is employed to set these indexes . When the

temperature rises , the spirit in the large bulb expands, and pushesthe index and column Ofmercury before it . When the temperature

falls, the spirit contracts , and the pressure Of the air- bubble in thesmall bulb drives the column Of mercury back, whi ch in turn pushes

the minimum index before it as soon as the temperature falls belowthat at which the inst rument was set . The defects Of the instrument are—it must always be kept in the vertical pos ition , otherwise


the Spirit may pass the mercury at the bends of the tube . The

m ercury tends to pass beyond the ends of the indexes so that smallquantiti es are retained by them .

Modern maximum and minimum thermometers are now always

distinct instruments . The student is advised to study these by

personal inspect ion at the show- rooms of a good meteorologicalinstrument maker .

Rutherford ’

s maximum thermometer consists of an ordinary

mercury thermometer, wi th an iron index introduced into the bore(mercury does not wet i ron) . With rise o f temperature the indexis pushed before the column of mercury ; with fall of temperature

the mercury at once parts company with the index . Th e l iquid ofthe minimum thermometer is alcohol , and the index glass (alcoholwets glass) . When the temperature rises , the alcohol flows past theindex withoutfm ov ing it ;

’

when it falls , the index is carri ed by the

retreating surface of the alcohol by capillarity .

In estimating the weight of volum es of air and aqueous vapour atvarying temperatures and pressures , it is necessary to understand

aright .the meaning of density,

’ specific gravity,’ and relative

density .

’

Density is defined as the mass of unit volume (massbeingthe amount of matter as measured by inertia) ; Specific gravity isthe ratio of the weight of a certain volume at a given temperatureand pressure to the weight of an equal volum e Of a standard substance at the same temperature and pressure . Since the unit

Volume is I c . c ., and the un it mass I gramme, i t follows that water i s

the standard substance whose density is unity . When the density

of oxygen is Spoken of as I 6, it is meant that the specific gravity Ofoxygen is 16, hydrogen being taken as the standard ; the real

density (mass of I c .c . O) i s 00 014 gramme . It is preferable to usethe phrase ‘ relat ive density ’

of oxygen , etc ., and consider

“

it as

meaning the same thing as specific gravity when air o r hydrogen is

the standard . The atomic weights of gaseous elements such as H ,

N ,etc. ,represent their relat ive densities , whilst the relative densities

Of compound gases are represented by half their molecular weights .The relat ive density of O is 16, that of CO2 22 , H being the standard .

The relative density of air referred to the same standard isI 4

‘

47In hygiene it is customary in calculat ing the weights , etc .

, of gases

1 28 PRACTICAL SAN ITARY SCIEN CE

and this mult iplied by 0 -622= weight of aqueous vapour:grains .

The pressure of aqueous vapour is constant for.

a given temperature , whether it is in m ono or mixed with a gas or gases , and

varies directly, as has ah eady been stated , as the temperature .

Two other types of problem arise in connection with this subj ect— namely , (1 ) finding the weight of a volume Of air satur ated withvapour at a given temperature and pressure ; and (2) finding the

weight of a volum e of air parti ally saturated with vapour at agiven temperature and pressure .

Example 1 .— Find the weight Of a cubic foot of air saturated with

aqueous vapour at 62° F . and 30 inches Hg .

By the table Of vapour tensions it is seen that 62° F . corresponds

with 05 56 inch Hg . As the total pressure of air and vapour is

30 inches , the pressure exerted by the air alone must be 30 05 56,

or 294 44 i nches . The problem , therefore, resolves itself intofinding the weight of a cubi c foot of dry air at 62° F . and29

-

444 inches , and that of a cubic foot of aqueous vapour at62

° F . and 0 5 6 i nch .

(

5

12x

29

34144

x grains (weight of dry air) .

ggi X X 5668 6 x 06 22: 61 6 grains (weight of aqueous

vapour) .

the cubic foot of saturated air

524-

32 +O°

I 6 grains= 530-

48 grains .

Example 2 .— Find the weight of a cubic foot of air part ially

saturated with aqueous vapour at 62° F . and 30 inches , dew- point

being 50° F .

The dew - point is the temperature Of comple te saturation of the

atmosphere . I f the atmosphere be raised in temperature, itscapacity for holding aqueous vapour will be increased ; if lowered ,

this capacity will be diminished . When the temperature is lowered

below the dew- point , vapour is deposited in the fluid form .

Vapour tensions in the above table correspond with temperatures

of complete saturation or dew- points , hence, in problems of the type

A IR 29

unde r consideration , if the dew—point be not given , it must be found .

This may be done directly by such instruments as Daniell’s or

R egnault ’s hygrometers , or indirectly by Glaisher’s formula

,or by

Apjohn’

s formula .

In the indirect method the wet and dry bulb thermometer are

used . By Glaisher’s formula the dew—point= D —G(D—W) where

D = temperature Of dry bulb, G= Glaisher’

s factor for reading Ofdry bulb , andW= temperature of wet bulb .

By Apjohn’

s formula

For temperatures above 32° F

For temperatures below 32° F

Where

P pressure Of aqueous vapour at dew- point .p pressure Of aqueous vapour at temperature Of wet bulb .

d difference in degrees F . between dry and wet bulbs .

h height Of barometer in inches .

Returning to the problem , when the dew—po int 50° F . has been

found, the pressure of the aqueous vapour 0 -

361 inch is obtainedfrom the table of vapour tensions .The problem is resolved as before into two portions— v ia , the

weight of dry air at 62° F . and pressure 30 —O °

3OI inches, and theweight Of vapour at 62° F . and pressure 0-

361 inch .

iiix°‘

3

3

flx 5668 6 x o -622= grains

5278 3-

98= 53 I~7S grains .

Relative humidity represents the ratio between the weight of

aqueous vapour present in a given volume of air , and the weightof vapour which would be required to saturate the same volume

of air under similar conditions Of temperature and pressure, and

is expressed as a percentage.

1 30 PRACTICAL SAN ITARY S CIEN CE

Consider the last exam ple , in which the temperature i s 62° F

and the dew- point 50°F.:Relative humidity

pressure at 50° F . x5

5

5

—3xg x 5668 6 x 06 22 pressure at 50° F .

pressur e at 62° F . xgi

gxgi

g—Ix 5668 6 x 06 22 pressure at 62° F .

03 61d t

03 61 x 100or expresse as a percen age,

05 56

The composition Of the air expired from the lungs contrastedwith ordinary air demonstrates the invariable nature of the N andthe limits of variat ion of O and CO

649 per cent .

O rd ina ry Air. Expired Air.20 96 per cent . 16 -

4 per cent .

7 70 -04 46

The practically un iform composition of the air all over the earthi s maintained by variations Of temperature leading to variations of

volume and pressure , with resulting air- currents, diffusion of gases ,the above—named circulation affected by respiration of animals

,

transpiration of plants rain , etc .

Oxyg en is the most important constituent of the air, in that it is aprime necessity to life . Its quantity is diminished by respiration ,putrefaction , combustions of all types , and at high altitudes .

The estimation Of O may be readily carri ed out in the following

ways:1 . The nitri c oxide (NO) method .

This method, although it has been adversely criticized, yields ,in careful hands , excellent results . The reaction is represented by

the equation:

The NO2 i s soluble in water . There is a contraction of threevolumes Of the mixture for every one volume of 0, therefore one

third of the contraction represents the 0.

To a sample of air in a gas burette excess of nitric oxide preparedfrom Cu tum ings and HNO3 i s added . .The mixture is passed into


bulbs ; the first and largest contains alkali and pyrogallic acid (dissolve 160 grammes KOH in 130 c . c . water

,producing about 200 c .c .

Of solution ; in this dissolve 10 grammes pyrogallic acid:i f these proport ions are not adhered to , evolut ion o f CO may take place duringabsorption of O , and cause error) the second and fourth are empty ;whilst the third contains water to seal Off the atmosphere . The

reagent absorbs O and CO The graduated burette is supplied atthe upper end with a stopcock and a Short piece of fine pressure

tubing (carrying a screw clip) which connects it with the smallmanometer U- tube of the bulbs . In order that this piece of tubingmay be as short as possible , the bulbs are raised on a block , so thatthe end of the manometer- tube is near to the burette . The burette

and the levelling—tube containing water are connected at their lowerends by rubber tubing .

In making an estimat ion , first mark on the ivory slip the height

at which the coloured liquid stands in the capillary U- tube , turn thestopco ck so that connect ion is made between the burette and bulbs ,then raise the levelling—tube unt i l all the air is driven over out ofthe burette into the bulbs . Now connect the atmosphere withthe burette, and lower the levelling - tube unt i l a defini te quant ityof the particular atmosphere (say 25 or 50 c . c . ) is admitted . Then

make connection with the bulbs , and raise the levelling- tube unti l

this quantity of air is driven over into the absorpt ion apparatus .

Turn the stopcock off, screw down the clip , and unfasten the bulbsfrom the burette . Shake carefully for ten or fifteen minutes , re

unite with burette , and bring back the air by lowering the levell ingtube . Repeat these manipulations until a constant vo lume isobtained , when the liquid stands at the original mark in the U- tube

and the burette is levelled . The decrease in volume is due to the

O and COZ absorbed . Deduct the COZ Obtained by Pettenkofer’

s

method ,and the remainder represents the O . This volume of O

is then reduced to standard temperature and pressure .

Since the temperature should not vary during the Operation , the

burette must not be handled . The absorpt ion reagent in the first

bulb,the water in the third , and the water in the burette , should

all be saturated with air before commencing the estimat ion . It is

to be noted that the pyrogallic solut ion w i ll absorb besides O othergases

,such as H S, 502, HCl , etc .

A IR 1 3 3

3 . Where accurate estimations are required , the combustion

method ofDumas may be used .

A measured volume Of air is drawn through KOH to free it fromCO2, and thence over ignited spongy COpper in a combustion

- tube .

The copper fixes the O,and the amount of the latter i s estimated

from the difference in weight of the Copper and Copper oxide .

Carbon Dioxide .—Carbon dioxide may vary in an atmo sphere

from 0 -2 to or 0 -8 per cent . The quantity ordinarily found in

a pure atmosphere ranges from 5 to 0 -04 per cent .

The atmosphere Of London during a fog often contains 00 8 percent . In a living - room lighted by coal - gas the COZ may reach

02 per cent ., with an appreciable amount of CO.

Carbon dioxide arises from (1 ) animal respiration ; (2) combustion of all kinds Of fuel ; (3) o rganic combustion in the form of

putrefaction , fermentation , etc . Its special Significance lies in thefact that as a product of respirat ion , it can be made a fairly accurate

measure of the organic impurities which accompany it .

Carbon "dioxide per se , in the quantities commonly found , may

be considered harmless . It is generally agreed that the amount

furnished by respiration may not exceed 00 2 per cent . Taking

0 -04 per cent . as the average quantity found in the air, 0 -06 per cent .

+ 0-04) will represent the limit of CO2 allowable in any atmosphere contaminated by respiration .

The num ber of cubic feet Of fresh air required to dilute the CO2Of a room , so that this limit may be preserved, will be found by the

formula:cubic feet CO2 added x 100

0 -02

The quantity of CO2 added to the air through respiration is,

roughly, 06 cubic foo t per head per hour . Substituting this figure

in the formula , i t is found that cubic feet fresh air per head

per hour must be admitted to living - rooms if the CO2 is to be keptwithin the limits named .

The Estimati on of C02 in the Atmosphere— Pettenkofer’

s M ethod.

When CO2 is shaken up with baryta water insolubleBaCO3 is formed, and the alkalinity of the fluid is lessened .

Take a 5 - litre air- j ar , cleansed and filled with water,into the

134 PRACTICAL SAN ITARY SCIEN CE

apartment in which the estimation is to be made . Pour out the

water so that the air may enter the j ar,and stopper carefully .

Prepar e baryta water by adding about 5 grammes Ba (OH) 2 toa litre o f dist illed water

,and accurately est imate

,in terms of

standard oxalic acid solution,the alkalinity Of 25 c .c .

, using phenol

phthalein as indicator . The acid is prepared by dissolv ing

grammes of the crystals in a litre . This solution is of such strengththat I c . c . i s equivalent to 0 -

5 c .c . CO at standard temperatureand pressure .

Now add 50 c . c . of the clear barium hydrate solution to thecontents of the j ar, and roll it round the interior for some time .

When , in say twenty minutes , the whole of the CO2 is absorbedand neutralized , take out 25 c . c . of the solution with a pipette and

rapidly titrate it with the stand ard oxalic acid, del ivered from aburette . The difference in alkalinity Of this and the original 25 c . c .

multiplied by 2 i s equivalent to the CO2 in the j ar in c . c . at N .T .P

Reduce the volum e of air in the j ar to and calculate thepercentage of CO

2on this .

The following is an example:Temperature 15°C . , pressure

750 millimetres . Twenty—fiv e c .c . of the freshly prepared Ba (OH)2were measured by pipette into a porcelain basin , a few drops of

phenolphthalein added , and standard oxalic acid run in until the

pink colour j ust disappeared after thorough st irring ; 2 1 -

5 c . c . of

the standard acid were used .

Fifty c . c . Ba (OH ) 2 were run into the j ar, and after completeabsorption of the COZ had taken place , 25 c . c . were removed and

titrated with acid ; 199 c .c ; standard acid were used . 2 1 5 19-

91 -6 c .c . ; and I 6 c . c . x 2 : 3

-2 c . c .= the total amount of acid equiv a

lent to the CO. in the j ar . But each c .c . O f acid= 0 ~5 c . c . C02 ;

therefore 3 2 x 0 -

5 = c .c ., the volume o f COZ in the j ar, or 1

-6 c .c .

in c . c . c . c . 50 the volume displaced by theThe volume of this c .c . at 0° C . and 760

° millimetres

4950 X 750

760 x {I-0036 x

( in the C . scale 5 3 or coefficient of expansion of gases

degree) c . c .

I -6 c .c . COZ in c .c . air: 0 -03 per cent .


When, from respiration , CO2 rises above per cent . , a certain

unpleasant odour is experienced in rooms , due to the accompanyingorganic exhalations , and when much above this figure headache

and even faintness may supervene . Volatile fatty acids exhaled

from the skin and H S are responsible for most of these unpleasant

odours .

A cubic foot of coal - gas yields on combustion 06 cubic feet COZ.

It is Obvious that when CO2 i s due solely to the combustion o f

coal - gas the quantity may be allowed to exceed considerably the

above—named limit .

CarbonMonoxide — This odourless gas possesses a special affinity

for haemoglobin , displaces oxygen from it , and thus destroys the

oxygen - carrying function of the blood and ultimately li fe , by cutting

short internal respiration . When haemoglobin is saturated to theextent of 30 per cent . , symptoms of poisoning set in , and 70 per cent .

saturation is fatal . Coal - gas contains by volume about 6 per cent .

CO, and when imperfect ly burnt leaves small quantiti es in the flue ;but greater danger attaches to the escape of the gas from ill- con

structed taps and j oints . The use of coke , especially i n cast - iron

stoves , is a fruitful source of CO . As CO2 passes over hot coke it i sreduced according to the equation C + COZ= 2CO.

The carbon of the hot cast - i ron acts in the same manner, reducingCO2 to CO. Solid particles o f organic matter floating in the atmo

sphere become charred on the exterio r of the stove , and this partial

oxidation results in the formation of CO. This gas is present in

tobacco smoke .

The characteristic cherry- red colour of CO- haemoglobin serves as

an excellent test for the presence of carbon monoxide . I f a fewdrops of fresh mammalian blood be diluted wi th water down to

about 2 per cent ., and the solution shaken up with CO, the distinc

t ive colour is at once formed . If dilution be extended to 0 -2 per

cent .,and HbCO formed by shaking with the gas , the characteristi c

Spectrum consisting Of two bands between D and E occupying nearly

the same position as those of HbOz, but differing in that they do no t

disappear on the addition of reducing agents such as (NH4) 2S or

H2S, may be readily seen .

HbCO may also be distinguished from HbO2 by adding to 10 c . c .

of the blood solution 10 to 15 c .c . 20'per cent . solution K

4Fe (CN) 6

AIR I 37

and 2 c .c . acetic acid (1 volume acetic acid + 2 volumes HZO) . A

reddish - brown: HbCO greyish- brown precipitate= HbOz.

The estimation ofCO in the air may be performed by ( I ) Haldane’

s

haemoglobin percentage saturation method , or (2) by the cuprouschloride method for large quantities .

1 . The following is Haldane’

s account of his method:A solut ion of about I of nOrm al blood to 100 of water is made ;

also a solution of carmine dissolved with the help Of a little ammonia ,and diluted till its depth of tint is about the same as that of the

blood solution . Two test - tubes of equal diameter (about dl, inch)are then selected . Into one o f these 5 c .c . Of the blood solution are

measured with a pipette ; into the other about an equal quantity

is poured . Ordinary lighting gas is then allowed to blow into thesecond test - tube through a piece of rubber tubing for a few seconds .

The test—tube is then quickly closed with the thumb before the gas

has time to escape , and the blood solution thoroughly shaken up

with the gas for a few seconds . The haemoglobin is thus completely

saturated with carbonic oxide, and the solution has now the char

acteristic pink tint . The carmine so lution , which has a sti ll pinker

tint , is now added from . a burette to the 5 c .c . o f normal blood

solution in the other test - tube until the tints are the same in the

two test - tubes . Not only , however, must the tints be equal in

quality, but they must also be sensibly equal in depth . If the

carmine“

solution is too strong or to o weak , the latter will not be

the case , and the solution must be diluted or made stronger acco rdingly. It is usually easiest to make the carmine a litt le too strong atfirst , so that on adding both carmine solution and water equality

can be established . From the amount of water which is required

to be added it is easy to calculate the extent to which the original

carmine so lution needs to be diluted . The so lutions are now ready

fo r use , and the actual analysis is made as follows:5 c . c . of thesolution Of normal blood are measured into one of the test—tubes ,and a d10p of the suspected blood placed in the o ther test—tube andcautiously diluted with water till its depth Of tint is about equalto that of the normal solution . If carbonic oxide be present in

the haemoglobin , a difference in quality Of the tints of the tw o solutions will now be clearly perceptible .

"

Carmine so lut ion is thenadded from the burette to the normal blood, and water (i f meces


sary) to the abnormal blood , t i ll the tints are equal in both qualityand depth . The carmine is added by about 02 c . c . at a t ime

,the

points being noted at which there is j ust too little and j ust too muchcarmine , and the mean being taken . The solution ofnormal blood

is then saturated with coal—gas , and the addit ion of carmine to theother test - tube continued unti l equality is again established andthe am ount Of carmine noted . The percentage saturation with

carbonic oxide of the abnorm al blood can now be easily calculated ,

since we know how much carmine solution its saturation represented

as compared with what complete saturation represented .

The method of calculation is illustrated by the following example:To 5 c .c . of normal blood solution 22 c . c . o f carmine is

required to be added to produce the tint of the blood under examinat ion , and 6-2 c . c . to produce the tint o f the same blood fully saturated . In the fo rmer case the carmine was in the proportion Of2 -2 in 7

-2 , and in the latter of 6 -2 in 1 1 2 . The percentage saturation

(x) Of the haemoglobin w ith carbonic oxide is thus given by the

following proportion sum:

100 :x.

x is therefore= 55 ~2 . As the compound of carbonic oxide and

haemoglobin is , to a slight extent , disso ciated when the blo od isdiluted with water , the value found is a litt le too low . The cor

rections needed are as follows:Add 05 i f 30 per cent . saturation

be found , I'I i f 50 per cent .

, 1 6 i f 60 per cent ., 2 6 i f 70 per cent

4 4 i f 80 per cent . , 100 i f 90 per cent . Thus , in the above examplewe must add 1 3 ,

so that the true saturation is 56-

5 per cent . In

comparing the tints,the test - tubes should be held up against the

light from a wi ndow, but bright light should be avoided as muchas possible , as it increases the dissociation . Failing daylight , an

incandescent burner, with a chimney of blue glass and an opal

globe, may be used as the source of light .

Haemoglobin brought into intimate contact with air containing00 7 per cent . ofCO will finally reach a state o f equilibrium in which

it is saturated to an equal extent with CO and oxygen . I f the

percentage of CO or oxygen in the air be increased or diminished ,

there w ill be an exactly corresponding increase or diminution of


must , however , be first diluted tor im (o r with carburetted water

gas tor i m) with air . As it is quite easy to make this dilution with

perfect accuracy , the method is an exact one , and is not only rapid ,

but avoids the difficulti es and sources o f error connected with theordinary method Of determination by cuprous chloride , or by explosion .

’

2 . The Cuprous chloride method .

Cuprous chloride i s prepared from copper turnings , copper oxide ,and strong HCl, and dissolved in dist i lled water . This solutionabsorbs CO.

The air to be treated i s first freed from O and CO2 by passagethrough Hempel

’

s burette . The residue is slowly and repeatedlypassed into a second absorp tion pipette containing cuprous chloridein so lution . The bulb containing the copper salt Should be large ,the t ime fo r absorpt ion long , and the transference from burette topipette and v ice versa as often repeated as necessary to procure aconstant reading . The loss in volume , assuming that ethylene ,acetylene , etc . , are absent , represents the CO present . This methodis by no means reliable .

Ammonia is found in traces in all atmospheres . It is a product

of putrefaction,and although in small quanti ties i t seems to be

harmless , it should be regarded with suspicion , by reason of the

noxious bodies which accompany it . It is found in larger quantity

in air in immediate contact with peat . I t may be collected andestimated by aspirat ing a known volume of air through ammoniafree disti lled water , and afterwards distilling and Nesslerising .

Sulphur Dioxide, Ammonium Sulphide , and SulphurettedHydrog en are all present in the atmospheres o f cities , and are

hurtful to health and vegetation . Sulphur dioxide abounds where

impure coals are consumed, and H2S where organic decomposition

takes place . It is stated that 00 6 per cent . H28 in an atmosphere

is dangerous to life , and fatal accidents in sewers have been

attributed to this gas .

SO2 may be estimated by aspirating a large and known volumeof air through bromine water, and precipitating the HzSO4 thusformed with BaClz. From the weight of the insoluble BaSO

4Oh

tained the weight of 802 is calculated .

Sulphuretted Hydrogen may be detected by exposing to the air

A IR 14 1.

strips of hlter- paper moistened with lead acetate , and estimatedquantitatively by aspirating a known volume Of air through a

solution of decinormal iodine containing a little starch paste . Im

mediately the blue colour departs the aspiration is stopped .

1 -

7 milligrammes H2S correspond with I c .c . i t I .

HzS + 1

2: 2HI S .

Ammonium Sulphide .~—The violet colour produced by the inter

action of (NH4)2S and sodium nitro -

prusside may be utilized for

matching a standard solution with another containing an unknown

quantity of (NH4) 2S .

Chlorine may be absorbed in 10 per cent . KI solution , and the

liberated I estimated with v sodium thiosulphate . Brom ine may

be estimated in the same way:2Cl ZKI 2KCl 1

2.

3 5 parts by“weight Cl: 126 parts I , or 7 9 parts bromine .

Nitrous, Nitric, and HydrochloricAcids may be estimated byabsorption of measured quantities of air in water, and employing the

methods described in water analysis .

CarbOn'

Disulphide r—The vapourof C82 found in the air of indi a

rubber works is estimated by passing it into strong alcoholic potash .

This solution is then acidified with acetic acid, and finally neutralized

with CaCO3 . It is now diluted to twice its volume with water andtitrated with standard iodine solution (1 6 6milligrammes I per litre)and starch paste . One c .c . I==I milligramme C82. The reaction is

complete when a faint blue t int appears .

Chlorine and bromine are inj urious to human beings in dilution

of 01 part per and the following as noted:Iodine 05 part per 100 000 .

502 and HCl 1 0

H2S and NH I O 'O parts per

CO 20-0

Ozone .- Ozone , an allotropic modification of oxygen , 03 , is a gas

possessing an Odour of phosphorus and an irritating action on thecells of the respiratory and conjunctival mucous membranes . It is

produced by electric discharges over the s ea , and to a greater extentat night than in the day . It is stated that more ozone is found in


the winter (especially after snowstor ms) than in the summer . It i s

absent from the air o f towns , living - rooms,and foggy atmospheres .

Detection and Estimation of Ozone — Pi eces of blotting - paper are

soaked in a solution of K I and starch , and dried . These are then

suspended in a cage, which protects them from direct sunlight , dust ,and rain for twelve o r twenty—four hours ; where ozone is present , itliberates I , which forms a blue colour with the starch . 0

3+ 2KI

+HzO It should be remembered that NzOs,

H202, and Cl act in the same way ; that free iodine may be partiallyvolatilized, or in part form iodide or iodate of potassium ,

instead ofblue iodide of starch ; and that constant results canno t be expectedowing to the variability in the conditions of temperature , light , andmoisture .

Houzeau’

s test consists in moistening faintly red litmus- papers

with a solution of KI and exposing them to the air . I f ozone be

present I is liberated, and alkaline KOH is formed, which rendersthe paper blue . Ammonia and hydrogen peroxide are the only

other two gases which could produce this result . As H202 is

practically never present , NH3is the only other gas to be con

sidered . I f, therefore , a second piece of litmus - paper untreated byKI is expo sed at the same time , and if the entire colour is not due

to NH3 ,the difference in the shades of the two papers must be

furn ished by ozone .

The intensity of colour created by ozone acting on papers exposed

to the atmosphere may be matched by one of a series of ten papersforming a standard scale . Each pair of papers is exposed to a

known quantity of ozone . Measured quantities of air are aspirated

over the papers in tubes . I f the papers are suspended in the atmo

sphere , w ind currents , etc . , by bringing unequal quantities of air

into contact with them,will vitiate the results .

Hydrog en Peroxide .— Aspirate 20 to 100 l itres of air containing

H202 through 100 c . c . distilled water . To 10 c .c . of the water add

I drop of a 1 per cent . potassium chromate solution , 2 or 3 drops

of 25 per cent . H2SO4 , and 2 c . c . of ether . Shake gently fo r some

time ; perchromic acid is formed and goes into solution in the ether ,rendering it blue .

Phosphoretted Hydrogen.—When grades of ferro - silicon rich

in silicon (40 to 60 per cent . ) are exposed to water or damp air, a


atmosphere . Ammonia , ammonium sulphide , and various com

pound ammonias emitting foet id odours,sulphuretted hydrogen ,

and marsh - gas , are present in ever- varying quantities . Ground

air is very rich in CO2, especially in the autumn season of the year .

Ground air Should be excluded from all living - rooms,not only

because of its own impurity , but because where it is allowed entrance ,other more dangerous gases , such as coal - gas , sewer—gas , etc . , mayoften enter too .

A sample of ground air may be collected for examination thus:A hollow , sharp - pointed steel cylinder

,with many perforations ,

is pushed into the soil for a distance o f 4 to 6 feet . The upper endof the cylinder is connected with an air—j ar, and this in turn withan aspirator . The j ar being shut off from the cylinder, is first

emptied by the aspirator ; connection is then made , and the samplecollected .

B esides C02, which may reach 5 or 6 per cent ., small quantiti es

of NH3 , CH4 ,

H2S are usually found .

Qualitative Examination of Air for Noxious Gases in Larg e

Amounts.

Where the air Of factories , etc . , contains noxious gases , qualitative

examination is readily performed by aspirating large quantities ofthe air through pure water or other suitable solvent . Where , however, the gases are in considerable quantities , tests

‘may be applied

direct to samples Of the air in j ars . Occasionally the atmospheresurrounding chemical works

,etc . ,

contains such large quantities o f

Cl , HCl, SOz, etc that this direct method of examination may beadopted .

The fo llowing gases may be readily recognised by a few simplechemical tests:

HC1, CO N203 , HNO3 , 50

2,01, co , cs NH (NH4) 2S .

1 . Having collected a sample in an air- j ar, remove the stopper

and smell the gas . Replace the stopper quickly . Cl has a charac

teristic Odour . HCl has a faint odour of chlorine .

’

SO2 has a

characterist ic Odour, so also have NH3 , (NH4)2S, HzS, C52.

CO CO, N203 , HNO have no odours .

A IR 45

2 . Take the reaction by moistening a red and blue filter-paper

with water and rapidly inserting them in the j ar, fixing the ends

between the neck and the stopper . If doubt exist as to the effect onthe litmus- papers

,the reaction may again be taken when the gas is

dissolved in a small quantity of distilled water.HC1, C02, N203 , HNO3 , soz areacid .

NH3 , (NH4)2S are alkaline .

HzS , CO, CS2 are neutral .

Cl first reddens blue litmus—paper and afterwards bleaches it .

3 . Dissolve the gas in 10 c . c . of water by vigorous shaking , and

if the reaction be acid , to 2 or 3 c . c . of the solution add a drop or

two of AgNO3 solution . A white precipitate indicates

(a) HCl . Acidity marked ; precipitate marked and solublein (NH4)HO ; insoluble in HNO3 .

(6) C02. Acidity slight ; precipitate slight . Addition of

Ba'

(OH)2 produces turbidity , increased on further addition of a drop or two of (NH4)HO.

(c) 502. Odour characteristic ; acidity marked ; precipitatemarked , soluble in HNO3 . Two or three c . c . of thesolut ion from the j ar added to iodide of starch willdecolourize it . I f 2 or 3 c .c . of the same solution beheated with a drop of HCl, a granule of Zn ,Hz

S will beformed , which will darken lead acetate paper .

(at) No precipitate , HNO3 . Perform the brucine test ; also thediphenylamine test .

(e) N O precipitate , N203 (now HNOz) . Test for nitrous acid

with KI , starch , and HZSO4 ; and perform the meta

phenylene - diamine test .

4. If the reaction be alkaline , the gas is either

(a) NH3. Odour characteristic . To 2 or 3 c . c . of the solution

from the j ar add a drop or two ofNessler’s reagent , andthe well—known yellow colour is developed . Or

(6) (NH4) 2S . Odour characteristic . N essler’s reagent causesa black colour when mixed with the solution from thej ar . To a few c . c . add a drop or two of sodium nitroprusside , and a violet colour rapidly appears .

5 . If the reaction is neutral , one or other of the following ispresent

(a) HZS . Odour characterist ic . Lead acetate paper is darkened . Solutions of salts of iron , lead , and copper produce the dark- coloured sulphides of these metals .

10


CS.”A liquid at o rdinary temperatures . Set alight adrop on a porcelain slab , and note the yellow deposit ofsulphur left behind .

6 . The only gas which first reddens blue litmus -paper and then

slowly bleaches it is Cl .

Odour characterist ic . Suspend a moist KI paper in thej ar . Free I will be liberated and darken the paper ; laterthe darkened paper w i ll be bleached . Chlorine addedto a mixture of ferrous sulphate and potassium sulphocyanide produces a red colour .

Note the di fferences between H2S and (NH4) 28 . H

2S has a

neutral reaction , Odour of rotten eggs only, and forms nocolour with nitro -

prusside of sodium . (NH4) 2S has analkaline reaction , odour of rotten eggs and NH3 ,

andproduces a violet colour with sodium nitro -

prusside .

7 . CO is distinguished by absence of Odour , no reaction withlitmus

,and by the characteristic colour and spectrum when shaken

with blood .

Bacterio logy of the Air .—The number ofmicro—organisms in the

air is largely determined by the quantity of dust particles in it .

Bacteria adhere to and are carried by dust particles ; the types

found in air are fo r the most part chromogenic saprophytes , yeasts ,and spores of moulds . The num ber varies with the altitude

,date

,

and amount of recent rains , and other factors . Numerical deter

mination is of service as a means of comparing methods of ventilat ion . Gordon , in his report on the ventilat ion of the House o f

Commons, 1906, states that in the dust of the chamber there werepresent per gramme:Streptoco cci , 10 to B . enteritidis spora

genes , to B . colt, to total number of

bacteria , toHaldane found the number of bacteria in the air of book - binding

workshops per litre 6, cloth factories I I , tailoring workshops 12 ,

ropemaking premises 327 .

Andrewes has shown in his reports to the Local GovernmentBoard that in certain circumstances characterist ic sewage bacteriaare found in the air of drains and sewers . He has carefully studied

the characters of the organisms found in drain and sewer air:B . coli

o f drain air corresponds in characters with the same organism as


their upper and middle thirds by a bridge tube . Each of the upright tubes is plugged with an india - rubber stopper carrying a

pipette‘

which reaches to the bottom of the tube . The pipettes are

plugged above with wool . One pipette is graduated in tenths of ac . c . The tube carrying the other pipette has a I O c .c . mark on the

glass . Ten c .c . of a I per cent . solution of sugar in water are placedin this tube , and the apparatus is autoclaved .

When about to use , remove the plug from the pipette which dips

in the sugar solution , and connect the other pipette with an aspirator .

The aspirated air bubbles through the solution,into the first tube,

through the horizontal connecting - tube , down through the second

tube , and passes out through the pipette connected with the

aspirator . When sufficient air has bubbled through, gently aspirate

the sugar solution into the entry pipette to wash it ; then run theliquid through the connecting- tube into the second upright tube , and

so into the second and graduated pipette ; repeat this several times

so as to co llect all the bacteria that have been caught on the glass .

Now , by the graduated pipette, distribute the liquid into the various

culture media .

This method is suitable for large volumes of air, and supplies

plenty of material for sowing cultures . It is thus one of the best

methods for detecting pathogenic bacteria .

Suppose 250 litres have been aspirated and 20 colonies have

grown on a gelatin plate sown w ith 1 c . c . of the'sugar solution

'

20 x 10 xssi

o

o800 number of aerobic organisms contained in a

cubic metre of air litres = I cubic metre) .A simple method which may be made by careful manipulation

fairly accurate is that of plate exposure:Pour Petri plates of gelatinand agar . When solid , expose them to the air under examination

by removing their cov ers for selected periods— say fifteen to thirtyminutes . At the end of the period replace covers and incubate .

When organisms have developed, count and calculate to units ofarea and time—say per square foot per minute (area of a Petri dishM

2 where r is the radius) . If necessary, the v arious subcultural

methods may be resorted to for the identification of individualspecies .

CHAPTER XI

FOODS TUFFS

MILK.

SINCE the milk of the cow is used to a much greater extent thanthat of any other mammal, its composition and properties have

been much'

more thoroughly studied . Its liability to early decom

position and the fact that it forms an excellent culture medium for

bacteria render it necessary that the st rictest attention should be

paid to its production collection , and distribution:Composition of cow 5 milk:

Pe r Cent.Water 87

-

75Proteins 3 50

Lactose 46 0

Fat 3-

40

Ash 0 .

75

Our knowledge of the pr oteins of milk is still very i ncompleteThe application of ordinary and crude chemical methods to the

investigation of vital products necessarily leads to unsatisfactoryresults . The preparation of pure proteins is a most difficult task ,and the probabilities are that in many cases where it is thought

that a pure product has been isolated it is contaminated by re

agents .

The proteins o i the milks of different animals vary considerably .

On the addition of an acid to cow ’s milk or goat ’s milk , a curd or

clot composed Of casein is f orm ed, and it is believed that in thesecases the casein is chemically combined with the phosphates of the

alkaline earths . In human milk and the milk of the ass and mareno such clot is produced on the addition of acid . Here it is believedthat the protein is not combined with phosphates . B esides casein

,

a second protein (lactalbumin) is found in all milks . Storch de149

150 PRACTICAL SAN ITARY S CIENCE

scribes a muco - protein which he holds forms a gelatinous envelope

round the fat globules . Amylolytic and proteolytic ferments aresaid to occur in milk .

The protein molecule is highly complex , as evidenced by itsindiffusibility. Through the action o f enzymes in the presence O facids and alkalies these complex bodies are hydrolysed

,passing

through various intermediate stages (varieties of albumo ses) intodiffusible peptones . Further hydrolysis produces amino - acids .

The number of proteins in the milk of the cow has been variouslystated . Duclaux maintains that there is only one— casein , existing

in two forms , coagulable casein and non - coagulable casein . Ham

marsten describes two— casein , corresponding to Duclaux’

s coagu

lable casein , and lactalbum in , corresponding to Duclaux’

s non

coagulable casein . This observer admits that lactalbumin has the

propert ies of a true albumin , and closely resembles serum albumin ;but holds that , owing to differences in certain physical constants ,it is a dist inct body . Hammarsten

’

s casein and Halliburton ’s

caseinogen are doubtless the same body . Sebele in describes a

globulin in milk .

Casein — When pure , this is a white , non - crystalline , odourless ,and tasteless substance , insoluble in water, weak acids , alcohol, andether . I t is soluble in stronger acids and weak alkalies ; It appears

to possess a peculiar affinity for calcium phosphate as it is almost ,if not quite

,impossible to free it from this salt . Casein contains

less sulphur than either globulin or albumin , but much more phos

phorus . In solut ion in weak alkalies it is laevo - rotatory on polarized

light . Béchamp holds that it is a weak dibasi c acid , forming two

types of salts , and his view is confirmed by Soldner . This body is

readily prepared by diluting milk about five times and adding aceti c

acid until the solution contains 01 per cent . The precipitate formed

carries down the fat with it . This precipitate is well washed on a

filter, dried by pressure , and dissolved in the least excess of ammonia . By this means the fat rises to the surface and the underlying solution can be siphoned off. It is again precipitated by

acet ic acid , washed , dried, and redissolved in a mm onia . Afterthree or four such precipitations the casein i s rubbed up withalcohol in a mortar . The alcohol is poured off, and the residue

treated in the same manner with ether . It is afterwards extracted


Mi lk contains traces of extractives and colouring matters . Its

characteristi c white appearance is held to be due to the interferenceof light rays produced by casein in pseudo - solution , a state in whichparticles exist in the solution not Of sufficient size to settle under

gravity , but whi ch interfere with the passage of light . These

particles can be separated by a current of electri city . There i s no

sharp line of division between crystalloids and colloids in solution ,substances in pseudo - solution , and bodies in suspension . In milk

,

fat is in suspension , casein in pseudo - solution , albumin in solution

as a collo id , and lactose i n solution as a crystalloid . The variety

in size of the particles or masses of molecul es probably determinesthe presence o f one or other of these states in a given case .

Lactose .—Lactose (C12H22

011

.HZO) is an aldose , and exhibits the

constitution o f a galactose—glucoside in that on hydrolysis by acids

i t produces a mixture of galactose and glucose . The aldehyde

group o f the galactose has been eliminated in lactose , whilst the

glucose remains .

Several modifications of milk- sugar are known , distinguishable

from each other chiefly by their action on polarized light . Lactose ,like other aldoses and ketoses , reduces alkaline solutions of CuSO4 ,forming cuprous oxide , the well- known Fehling

’s react ion . Each

sugar effects a definite amount of reduction , and this affords an

excellent method of distinguishing them . Lactose differs fromother sugars in that its osazone forms an anhydride soluble inboiling water .

Lactose is hydrolysed by a specific enzyme lactose found incertain torulae, i n some kefir preparations , and in aqueous extractof almonds . Lacto se is not hydrolysed by maltose , i nvertase, ordiastase . It easily undergoes lactic and butyri c acid fermentations .

Mineral acids hydrolyse it to glucose and galactose . It reduces

Fehling ’s solution , and exhib it s mutarotation . It is manufactured

by evaporati on of whey, the resulting crystals being purified by re

crystallizat ion .

Fat of Milk—The fat Of milk consists of a mixture of etherealsalts of glycerol , forming small globules ranging in size from0 001 millimetre to 0 01 millimetre .

It is highly probable that there are three separate acid radiclescombined with each glycerol group, thus:

M ILK I S3

/C4H702C3H5

_ C18H3302C18H35OZ,

a compound of the acid radicles,of butyrin , and stearin

glyceryl .Milk—fat has the following composition:

P ce r ent.

Butyrin 3-

90

Caproin 3-

45Caprylin 0 -

50

Caprin 1 -85Myristin 20-

30

Laurin 7-

50

Stearin 2 -00

Palrnitin 25-

50

O lein 35-00

In addition to'

the above fats , traces of certain extract ives , suchas urea , lecithin , cholesterin , together with colouring matters ,exist in the fat ofmilk .

The vexed question of the presence or absence of a definite membrane round the fat globule wil l not b e discussed in this work . It

may be stated in a word that B échamp from his studies of theappearances found on mixing ether with milk and of the behaviour

of milk towards certain stains has concluded that an endo smotic

membrane exists ; whilst Storch by his observations is led to believ ethat instead of a definitemembrane a muco - protein capsule encloses

the fat globule and insensibly shades off into the surrounding fluid .

Human milk has the following composit ion:

WaterFatCaseinAlbuminLactoseAsh

The fat globules are smaller than those of cow’s milk, rangingfrom to 00 009millimetre . Its composition vari es much morethan that of cow

’

s milk . It contains small quantities of citri c acid .

I t is ahn ost always alkaline .

When milk is allowed to stand for a time, a series of well- known


changes succeed each other . The fat , the lightest portion , rises tothe surface as cream . After a variable period ,

depending on the

temperature , presence of certain micro - organisms,and other factors ,

the milk becomes acid and separates into solid curd and liquid

whey. The principal agent in thi s reaction is the B . lacticus,

which converts lactose into lacti c acid . Other micro - organisms ,such as the B . butyricus , B . coli commun is , etc .

,are also capable of

forming acid , and thereby curdl ing milk . Rennet is used art ificiallyfor bringing about the same change . The curd consists of precipitated proteins with entangled fat , and the whey of water, lactose ,and salts . The cream of ordinary milk forms about 10 per cent .

by volume of the whole .

The variations in the composition of milk , even from the sameanimal , are due to a number of factors , such as the health of the

animal , the age— young animals secrete less milk and a product ofpoorer quality— the t ime that has elapsed from the last milking ,the stage of milking , the breed of the animal , the t ime that haselapsed since previous parturition , the nature o f the food eaten , etc .There are , however , limits to these variations , and all good milksat all times fall within these limits . Fatty solids may range from2 to 7 per cent .

, non - fatty solids from 8 to 1 1 per cent ., ash from

0 -6 to 0 -

9 per cent ., cream from 2 to 25 per cent .

, specific gravityfrom 1 0 27 to 1 0 37 .

But it is rare that the fatty solids fall below 3 per cent . , and the

non—fatty solids below 8 5 per cent . , and these figures are insisted

upon by law .

Comparative analyses of various milks are represented in thefollowing table:

Wate r . Pro te ins . Lactose . Ash.

Cow 87 7 3-

5 4 6 07Human subj ect 88 2 1 5 6 8 0-2

Goat 86 -0 4-

3 4 2 0 -

7Mare 89

-8 1 -8 6-

9 0 3Ass 90

-1 I‘O 6 -

5 0 -

4Ewe 794 6-

7 4-

3

In cattle - plague and foot - and-mouth disease marked changes

occur in the milk of the animals affected . The quantity is dimin

ished , the curd separates out quickly on heating from a pale blue

whey, and blood and pus corpuscles are generally pres ent . In

156 PRACTICAL SAN ITAR Y S C IEN CE

by immersing a plummet of known volume in the liquid , and noting

the loss of weight due to the displacement of the same volume ofliquid— example , Westphal

’s balance . The second method is

applied by immersing a float of known weight in the liquid , and

noting the volume immersed,which will be equal to a volume of the

liquid Of the same weight as that of the float— example , hydro

meters , o fwhich the lactometer is a special form used in testing milk .

In using the specificgravity bottle , which is perhaps the most

exact method , care should be taken that the bottle is clean . It is

well to Observe the ritual of subj ect ing the bottle to cleansing withweak acid , water, alcohol , and ether on each o ccasion before use ,and to weigh it direct from a desiccator . The bottle is first weighed .

It is then filled with milk,the stopper is gently let in , and its hollow

channel is filled to the top with the fluid . Any superfluous milk

is carefully wiped away with a clean and dry duster , and the bottle

is again deposited in the desiccator for a Short period before weigh

ing a second time . The temperature should remain constant andat 155

°C . during the entire process .

The second weight minus the first is equal to the weight of the

milk contained in the bottle . This weight divided by the weightof the same volume of disti lled water at the same temperature isthe specific gravity . Most specificgravity bottles have the weight

of dist illed water which they contain at 15 5°C . marked on their

surface , so that it is unnecessary to take this weight”Taking the specific gravity of H

20 at 155°C . as I '

OOO, that o fmilk is about 10 32 . It is obvious that the removal of fat whichis the lightest constituent o f milk raises the specific grav ity ,

and

its addition lowers it . The addition of water also lowers the specific

gravity . So therefore a low Specific gravity may mean either abun

dant fat or added water .

The specific gravity of milk is Observed to rise slightly for some

hours after milking a milk of specific gravity 1 0 31 when

drawn from the cow may in ten hours show a Specific gravity of

1 0 32 this rise is known as Recknagel’

s phenomenon .

’

I f the quantity of cream as measured in a cream - tube reading

percentages be the normal 10 per cent . after standing twenty- fourhours , and the Specific gravity be found low , it is clear that water

has been added .

M ILK I S7

The Westphal balance consists of a graduated swinging arm

resting on a knife - edge and a glass plummet suspended from ahook attached to one end of the arm . The other end of the armis drawn out to a point which when the balance is adj usted and

the plummet hangs in air should rest exactly Opposit e a similar

point on the frame . Three riders are used on the graduated arm:their weights are wholly empirical , and indicate hundreds, tens,and units respectively .

The milk or other fluid is poured into a glass cylinder ; the arm

is raised or lowered by means of a screw in the upright support

until the plummet is j ust completely reversed , and the riders are

so placed on various divisions of the scale that the points come torest exactly opposite each other . Supposing that in an estimation

the largest (as’must be) is suspended from the hook carrying the

plummet , the tenth division of the scale , and the tens and units

riders rest on the scale divisions 3 and 2 respect ively, when the

point of the swinging arm comes to rest at zero the specific gravity

will be 100 x 10 + 10 x 3 + 1 x 2 = I-O32 .

Lactometers , Special forms of hydrometers , are less accurate inestimating Specific gravit ies .

The specific gravity ofmilk varies between 1 0 13 and 1 0 39.

By removal of all‘ the cream from a milk of specific gravity 1 0 32 ,

the figure is raised to On the other hand, by'

adding 4 per

cent . fat to the same milk, the specific gravity is reduced to 1 0 28 .

The specific gravity test is not an absolute one , but a useful preliminary test . Like most substances , milk alters in specific gravitywith change of temperature . It does not share, however, the

peculiarity which water possesses of attaining its maximum specific

gravity at 4°C . It decreases in specific gravity from freezing

point C . ) upwards . Tables of corrections for temperature

have been constructed when the determination is made at tempera

tures above or below 155°C . ; but it will be sufficiently exact to

add or subtract I degree of specific gravity for every 6 degrees oft emperature registered above or below 155

°C .

The Fat.—Oi the many methods at present in use for the estima

tion of fat , the following two are to be recommended, and the first

is preferable to the second:I . ADAMs

’

s PROCEss .

- In this gravimetric method the solvent


used for the extraction of fat is ether , convenient on account of itslow boiling - point and heat of volat ilization , its high solvent power

for fat , and its miscibility with water .

When milk is dropped O11 blotting- paper , it spreads out to a much

greater degree than when placed on glass or in a dish , and Adam


entrance of moist air which would slightly wet the ether . In drivingo ff the ether from a flask , i t is well to lay the flask on its side in oneof the openings o f the water- bath , and afterwards , when the drying

is being completed in an air oven , the flask should be rotated from

time to time , and air blown in every fiv e minutes , to remove ethervapour .

Dry ether is prepared by washing commercial ether with water,shaking the washed ether with calcium chloride

,and , after allowing

it to stand over calcium chloride for a day or two ,distilling .

FIG . 2 7 .

A , Ev aporating basin ; B , specific- grav ity bottle ; C , fat flask ; D , p ipette

E , boiling - tube ; F ,100 c.c. stoppered cylinder .

Sufficiently dry ether may also be Obtained for most purposes by

dist illing the comm erical variety and rej ecting the first fractions

which pass over below 343°C . , and the last above 348

°C .

I f at any time doubt exists as to the completion o f the extraction

process,a second weighed flask containing fresh ether should be

afli xed,and the process continued for some time . This flask after

evaporating the ether and drying at 100° C . should not increase in

weight .

2 . THE WERNER - SCHMIDT METHOD — The specific gravity Of thesample is ascertained or a measured volume is weighed . Fi fteen c . c .

M ILK 6 1

are pipetted into a boiling- tube and a like measure o f pure hydrochloric acid added . The mixture is shaken up and gently boiled

until the contents appear dark brown in colour . The boiling must

not be continued too far, as certain bodies soluble in ether are liableto be fo rmed from the milk- sugar . The process is not suitable formilks containing cane - sugar . B oiling with acid renders the casein

soluble , and so eliminates the Obstacles which , in the solid condition ,it offers to the extraction o f fat .When cold, pour the contents of the tube into a graduated

and stoppered I oo c . c . cylinder . Wash out the tube with ether,

and finally make the column up to 75 c .c . with ether . Inv ert the

cylinder several times , and put aside to settle . Read the height ofthe ethereal colum n , including three- fourths of the thin grey layerof casein . Draw off an aliquot part of this column and evaporate ;dry

,and weigh the residual fat in a small flask , in the manner

described in Ada'

ms ’s process .

Stokes ’s tube, a Specially graduated tube prepared to treat10 c .c . of milk , is also employed in this country . After complet ing

the boiling with 10 c . c . ofHCl, and cooling , ether is added until the

surface of the column reaches the 50 c . c . mark . An aliquot portion

of this colum n is afterward s drawn off, evaporated , dri ed , and the

residue weighed as above . The Special tube is not to be recom

mended, as the narrOwed central portion offers resistance to the

free escape of hot air during boiling, and the consequent explosiveact ion frequently causes loss of the contents .

This process is much more .rapid than that of Adams,and in

skilled hands almost as accurate .

The . student will remember that , owing to the low boilingpoint

of ether, it should never be added to a hot solution , and will accord

ingly always co ol the boi ling- tube before adding it . This may

be rapidly done by holding it under a water- tap . In drying andweighing the fat it is essential that the last trace of ether vapourbe got rid of by blowing dry air into the flask , and by ascertaining

that two successive weighings , separated by half an hour’s heating

at 100° C ., are the same .

Example s—A milk whose specific gravity is 1 0 32 is subjectedto the Adams process , and the fat collected in a flask weighing

1 1


160 56 grammes . The weight of the flask and fat is 162 36 grammes .

The weight of the fat i s therefore gramme .

5 c . c . of specific gravity I °O3Z grammes .

I f now 5 16 grammes ofmilk yield 01 8 gramme fat , what is thepercentage of fat

5-16 100 0 -18 the percentage .

Percentage therefore = 3 -

5 nearly .

The same sample subj ected to the Werner—Schmidt processyi elded practically the same result .

15 c . c . of the milk yielded 0 -

542 gramme fat ;but 15 c .c . of specific gravity = I 5

-

48 grammes ;100

3 . There are several forms of centrifugal apparatus used for estimating fat , such as the Babcock , Leffmann -B eam , Gerber, etc .

The Leffmann-B eam provides small flasks graduated on the neck

into eighty divisions— ten divisions corresponding to 1 per cent . of

fat . Run into the flask I 5 c . c . milk . Add 3 c . c . of a mixture ofequal parts HCl and amyl alcohol ; shake and add slowly with

agitation 9 c .c . concentrated HzSO

4. Fill Up to zero with hot mix

ture of equal parts concentrated HzSO4 and water . Place in thecentrifuge and rotate fo r two minutes . If fat and acid liquid arebo th quite clear, read off the fat colum n ; i f fat or acid liquid becloudy , rotate again . The amyl alcohol assists in the collection of

the fat globules:this reagent should be good, o therwise large '

error

may occur,generally in the direction of excess of the truth . Where

the operation is carefully carried through with sound reagents resultsare obtained to within 0-15 per cent . of those got by the Adams

’s

proces s .

The reagents used in the Gerber process are HzSO4 and amyl

alcohol . The centrifuge runs on ball bearings , and reaches a velocityof about revolutions per minute . Three minutes are sufficientto separate the fat .

In the Babco ck method HzSO4 and boiling water are employed

as reagents . The centrifuge revolves at about times per

164 PRA CTI CAL SAN ITAR Y S CIEN CE

w ith sufficient draught ; here the drying is completed . It may

require two to three hours in the oven to produce a constant weight .

Plat inum basins are preferable to'

po rcelain , as they cool much

more rapidly , and thus require less time in the desiccator . As milk

solids are highly hygroscopic , no time must be lost in conveyance

from the desiccator to the balance , nor in the process o f weighing .

Supposing that the Specific gravity o f the milk is I -o32 , the weight

o f I O c . c . will be grammes . Further, supposing the difference

in the first and second weighings of the dish to be 1 3 grammes ,the percentage of total solids will be found from the propo rtion:

10 -

32 I OO 1 -

3 x ;

100 x 1 -

312 "

103 23 '

From the total sol ids the ash is obtained by ignition at a lowheat over an argand burner . The last trace of dark , separated

carbon must disappear and the residue consist o f a greyish -white

mass before the dish is removed from the flame . Overheatingcauses loss ofNaCl . Cooling , weighing , and percentage calculation

are carried out in the usual manner .

TheP and S of the milk proteins produce phosphoric and sulphuric

acids . Carbonic acid is formed by the combustion of organiccarbon . The ash does not truly represent the inorganic consti

tuents . It is computed that at least 8 per cent . of the phosphoric

acid arises from the P of the casein . Bases predominate over acids

in milk , and unite with proteins to form soluble protein salts , and

with citri c acid to form citrates .Composition of ash:

LimePhosphoric acidPotashChlorineSodaFerric oxideMagnesiaCarbonic acidSulphuric acid

A probable composition for exist in

been theoretically calculated:

M ILK

Per Cent.NaclKCI 9

~I 6

KH P04 I 2 '

77K2li poi 9 22

K2

6 6(C H5

4

70

MgHP05

4 3‘

7 I

Mg6 (C6H507)CaHPO4 7

’

42

Ca6 (PO4

Ca6 (C6H5

2

0Lime combined with proteins 5 1 3

If the ash IS materially less than 07 3 per cent . , watering may besuspected .

Solids notFat. —This item of the analysis is calculated by findingthe difference in weight between the total solids and the fat . The

solids not fat have been found to vary between 5 and I O per cent .

The law fixes 85 as the lower limit fo r whole milk .

In case it is necessary to determine the percentage o f proteins

in milk , the best method to employ is the following modification of

Kj eldahl ’s method for the estimation of total organic nitrogen , and

multiply the result by 63 8. To obtain the total organic nitrogen ,weigh 5

'

grammes of milk into a Kj eldahl flask of about 150 c . c .

capacity, and add 20 c .c . pure HzSO

4. Place over a small flame in

the fume - chamber, and heat ti ll thoroughly charred ,. Remove the

flame, and add I O grammes bisulphate of potash to raise the boiling

point of the mixture . Place a pear - shaped bulb in the neck of theflask and apply the flame, increasing its, size as frothing ceases . The

liquid becomes colourless in thirty minutes o r thereabouts . Co ol ,dilute largely with water, and transfer to the distillation - flask pro

v ided with perforated co rk carrying a dropping funnel with stopcock , and a wide tube with one o r more bulbs blown in it , which

are loosely packed with asbestos . One end of the tube is connectedwith a condenser, and the other is made to dip below the surface of50 c . c . {

I

6 HzSO

4.

Through the dropping - funnel pass about 100 c .c . of a 20 per cent .

solution of NaOH . Shake well by a rotatory motion . Apply aflame to the distilling - flask and collect about 200 c . c . of the dis

tillate . Take care that the condens er remains throughout quitecold . Titrate with

l

N

6- N ,aOH using litmus as indicator . Subtract


the number o f c . c . {6 NaOH solution used from the 50 c . c . firsulphuric acid , and the remainder represents the acid neutralizedby the ammonia distilled over . From this deduct the figure obta ined in a blank experiment in which all the factors are exactly the

same , except that milk is eliminated .

Each c . c . of the {6 HZSO4 neutralized by ammonia is equal to00 014 gramme of N , which , when multiplied by is equal to

the total protein .

Colostrum is a term applied to the first milk secreted after parturition . Houdet describes two forms— a viscous , brownish product ,and a non - v iscous lemon -

yellow liquid ; the earlier milkings furnishthe first , and the later the second ; the two co - exist often in thesame animal . The fat di ffers somewhat from that of ordinary milk ,

in that its melting -point is high (42°C . ) and its Reichert—Wo llny

figure low (6 to The mo st characteristic feature of colostrumis the presence of the corps granuleux of Donné, consist ing of cells

clustered together like bunches o fgrapes , and measuring in diameter

from 00 05 to 00 25 millimetre . The specific gravity of colostrum

av erages I °O68.

Estimation ofCitricAcid in Milk.— Prepare acid nitrate of mer

cury by dissolving mercury in twice its weight of HNO3 (Specificgravity and adding an equal volume of water .

With this reagent precipitate the proteins o f the milk , and filter

until the filtrate is clear. Rapid clearing may be effected at thisstage by addit ion of some super- saturated solut ion" of aluminiumhydrat e . To a measured volume of the filtrate add dilute caustic

soda so lution until the neutral point is reached (phenolphthalein asindicator) . Filter off the white precipitate of calcium phosphate ,calcium citrate

,and mercuric nit rate ; wash well with water ;

remove from the filter,and suspend in water , to which a litt le

dilute HCl has been added . Pass H2S through the fluid until

all the mercury comes down as HgS . Filter again , and boil the

filtrate to remove HzS . Add a little calcium chloride and cool .

Carefully neutralize a second tim e with dilute caustic soda , and

filter o ff the calcium phosphate . Concentrate the filtrate to small

bulk. This contains the citric acid as calcium citrate . After

thorough boiling , filtering , and washing the precipitate with boilingwater , ignite it , and add to it excess 96 HCl . Titrate back the excess


solut ion by dividing the normal rotation reading in angular degreesby . I ~106.

Principles of Polarimetry.— The vibrat ions which constitute an

ordinary light ray take place in all direct ions in a plane perpendicular to the line o f propagation of the ray . I f one looks at an obj ectthrough a crystal of Iceland spar, two images are seen— the light

ray has been Split by the crystal into two , the more refracted orordinary ray , and the less refracted or extraordinary ray . The less

refracted o r extraordinary ray does not obey the ordinary laws of

refraction , but presents an image which moves when the crystal

i s rotated . Both rays are said to be polarized consist now

o f vibrations in one direction only in the plane perpendicular to theline of propagation of the ray .

I f a crystal of spar be cut through its obtuse angles, the sectionspolished and cemented together, and the long sides blackened , a

N ico l prism is formed . Such a prism absorbs the ordinary ray

by the black sides after it has been totally reflected by the cut

surfaces , whilst it allows the extraordinary ray to pass through in

a direction parallel to the source of light .

A polarimeter consists of two N i cols mounted parallel to eachother— one , the polarizer, fixed ; the second , the analyzer , movable .

I f the movable prism is exactly parallel to the fixed , a beam of light

will pass through it ; if not exactly parallel , but inclined at an angle ,less light will pass through ; i f at right angles, all light will be cut off.

I f a solution of an Optically active substance be interposed be

tween the N i cols set parallel , the quantity of l ight passing through isdiminished, but the original intensity can be recovered by rotatingthe analyzing prism . The amount of such rotation is equal to the

power of rotation of the solution . In all polarimeters the analyzer

is mounted on a graduated circle, so that the number of degrees of

rotation can be easily measured .

The recognition of equal intensity of light in a polarimeter before

and after the passage o f light through an optically active solution is

very difficult , and readings are accordingly far from co rrect . To

overcome this difficulty, Laurent placed behind the polarimeter aquartz plate of such thickness that one of the two light rays pro

duced in it is retarded by half a wave length (and consequentlyreversed in direction) , and of such size that it covered

‘half the field .

M ILK -

169

The ray resulting from the blending of the affected and unaffected

rays accordingly emerges in a plane at an angle to the originalplane ; in other words , the polarized light , passing through the

quartz plate is rotated through an angle . Two sets of rays ofpolarized light at an angle to each other will accordingly reach the

analyzer . If the analyzer be arranged parallel to the light comingfrom the covered po rtion , this half of the field will appear light , and

the other half dark . On the contrary, if the analyzer be set parallelto the light coming from the uncovered portion , this half of the field

will appear light , and the other half dark . By adj ustment the

analyzer can be placed in a position in which the two halves appearequally illuminated . This position corresponds with the zero o f

the circular scale and with the zero of the vernier . With Laurent ’spolarimeter monochromatic sodium light is used , a cell containing

potassium bichromate being placed in front o f the polarizer to

intercept the blue rays .

The instrument consists of the following parts:B ichromate cell ,polari zing prism , quartz plate covering half field , trough to carrysolution under examination ,

I

circle graduated in degrees , a double

vernier attached to ana lyzing prism and moving on graduated circle ,and a telescope to focus edge of quartz plateWhen the active substance in solution is placed between the

N ico ls_

and equal illumination o f the two half fields restored, the

vernier will have moved in the direction o f the hands of a clo ck(dextro - ro tato ry) , or in the opposite direction (laevo - rotatory) .

The distance traversed measured on the circular scale gives the

amount of ro tation in degrees .The specific rotatory power [a ]D —that is , the rotation produced

by I gramme of the substance disso lved in I c . c . of liquid examinedin a tube I decimetre long (ro tatory power of 100 per cent . so lution)—being known , we can determine the strength o f an unknown

s olution .

For glucose [a ]D 52 lacto se + 52 sucrose galacto se + 82° ; fructo se—938

° at C .

The percentage strength of a solution is given by the formula

fl:

1 70 PRA CTI CA L SAN ITARY SC I EN CE

where [a]D = specific rotat ion for sodium , o r D light .

observed rotation on the circular scale .

concentration .

length of tube in decimetres .

PolarimetricEstimation of’ Lactose in Mi lk— Put60 c . c . milk

in a 100 c . c . flask ; add I c .c . mercuric nitrate (Hg dissolved in twiceits weight of HNO6, specific gravity , I -

4z + an equal volume of

H O) , and fill up to the mark with water . Shake thoroughly and

filter through a moist filter—paper . When quite clear , determinerotation in polarimeter . Make several readings , and take an

average . Co rrect for Space occupied by proteins and fat . The

volum e of the fat in c . c . is found by estimating its weight andmultiplying by and the volume of the proteins is found by

multiplying their weight by 08 . Water equal to the sum of these

volumes in c . c . is added to the 100 c . c .

The calculation involved by taking 60 c . c . ofmilk may be avoided

by taking a simple multiple of thestandard amount of the polari

meter used . Thus , in the case of an instrument adj usted so that

205 6 grammes lactose in 100 c . c . of solution produce 100 degrees

on the percentage scale , 61 -68 grammes (20 -

56 x 3 ) are weighed ,treated with mercuric nit-rate solution , and made up to 100 c . c .

The volumes of fat and proteins are calculated , and the sum added

to the 100 c .c . Finally the po larimeter reading divided by 3 wi ll

give the percentage of hydrated lactose .

Estimation by Fehling’

s Method .—This method depends on the

fact that , whilst Fehling’

s solution may be boiled w ithout change

if a small quantity of glucose or other reducing sugar be added

at the boiling temperature , a precipitate of cuprous oxide is formed ,

and that the amount of copper salt reduced is proport ional to the

quantity of sugar used . Prepare Fehling ’s solution . Powder and

press between blotting- paper to remove moisture crystals of pure

Copper sulphate (CuSO4 ,5HzO) weigh grammes ; dissolve in

water ; add 0 -

5 to I c . c . pure HzSO4 dilute w ith pure water to a litre .

Weigh 350 grammes Rochelle salt

CH (OH)°COOK

1um potassmm tartrateCHOH'COONa ,4HzO

and dissolve in about 700 c . c . water ; weigh 100 grammes NaOH

1 72. PRACTICAL SAN ITARY S CIEN CE

be used in very large excess , the oxide is kept in solution , as in

Pavy’

s modification . The end - point difficulty is perhaps best metby using Ling ’

s indicator:Dissolve in 10 c . c . water at 45°1 5 grammes

ammonium thiocyanate and 1 gramme ferrous ammonium sulphate ;cool immediately ; add 5 c .c . strong HCl when a brownish - red solution is obtained . The colour is got rid o fby adding a small quantityof zinc dust . To determine the end—point , remove a drop of the

reduced copper so lut ion , and mix it with a drop of the indicator ona white surface ; when a red colo ration ceases to appear , thereduction is complete .

Genuine commercial milk—sugar crystallized from water gives:Not mo re than 00 5 per cent . ash .

Solubility at 15°C .

= 7-0 grammes per 100 c . c . (with an increase of

O°

I gramme per 100 c . c . for each degree of increase of temperature) .

Fall of temperature , 05°C .

B irotation ratio , 1 6 .

Amount ofmilk- sugar , 99-

5 to 99-

9 per cent .

Milk- sugars are adulterated with cane - sugar, maltose , dextrose ,and Various mineral matters . Cane - sugar can be detected by

treating a solution with yeast at 55°C . for six hours . Milk - sugar

is unchanged in specific rotatory power, whilst the addition of as

little as I per cent . cane - sugar produces a marked change . Maltose

is detected by a decrease in the birotation rat io ; dextrose by anincrease in this ratio and a decrease in the fall of temperature .

‘

Adulteration of Milk.— The principal adulterations are the addi

tion of water and the abstraction of cream .

The estimation of the water added is made from the solids not

fat , as these solids , in different samples , do not depart so far from

the mean as the fat . The legal limit is 8-

5 per cent .

Example —A milk yields 3 per cent . of fat by one o f the foregoingprocesses of estimation , and I I per cent . of total solids . The solids

not fat amount to I I 3 = 8 per cent .

On the assumption , therefore , that per cent . represents 100

per cent . pure milk, 8 per cent . will represent 94 -1 per cent . pure

milk .

(85 8 :100

In other words , 59 per cent . of water has been added to this

sample .

M ILK I 73

It may be urged that , since a few animals produce milk con

taining less than 3 per cent . of fat and less than 8 -

5 per cent . of

solids riot fat , it is unfair to the dairyman to enforce these figures

as legal l imits . But the number of animals in a herd p roducing

milk below these standards is so small in proportion to the whole

number,that the mixed milks should in all cases not only reach

but surpass the standards .

Cane - sugar, starch , dextrin , and o ther bodies have been added

to mask the addition of water by raising the solids not fat ; thesemay be detected by the sweet taste , deficiency in total nitrogen ,and by the ash . Starch is denoted by the blue colour formed withiodine . Common salt has been added , and is detected in the ash

by increase of Cl . Chalk , carbonate and bicarbonate of soda ,borax , fluorides , etc. , may be found . Of these , borax and boracicacid are used as preservatives . The employment of preservatives— bodies such as boric acid , formalin , eta — that prevent the growth

of micro—organisms has been much discussed . Some hold that it

is’

better to add these bodies than to allow the milk to decompo se ;Whilst others advocate the exclusion of all such reagents .

There does not appear to be any experimental evidence to showthat small quantities of preservatives like boric acid and it s compounds exert an injurious effect upon healthy adults , or even uponhealthy children ; but in the case of weakly infants

’

there is a strong

feeling in favour of excluding all such bodies from their food .

Salicylic acid holds a somewhat different position . In quantities

necessary to prevent the growth o f micro - o rganisms this drug is

likely,“ in certain cases , to produce inj urious effects . B esides , it

i nhibits the action of the digestive enzymes of the alimentary tract .

Its use as a preservative has been rightly forbidden in France .

Form alin , formal , or formol is a 40.

per cent . solution o f formaldehyde in water , and in the strength of I per cent . has been much

used as a milk preservat ive . It produces a very decided change in

casein , rendering it insoluble in the digestive juices . A patentedprocess exists in Germany for converting casein

,

’

by the action offormalin , into a substance resembling celluloid . This preservat iveshould be rigorously excluded from all foodstuffs . The question

of the addition of preservatives to milk has another aspect. All

purchasers of milk expect to get a thoroughly fresh arti cle . An y


procedure allowed the dairyman by which he can retain milk fora number of days puts a premium on the sale o f a stale substance .

Mi lk should be consumed on the day on which it i s drawn from the

animal . I ts const itution i s such that , apart from sterilization ,

which can only be legitimately performed by heat , it rapidly decom

poses and becomes unfit for consumption . I f dairymen were com

pelled to keep their churns scrupulously clean , and the temperatureof the milk during transit sufficiently low , there would be no need

for preservatives , and we should hear little of decomposed milk .

It is stated that a mixture of boric acid and borax is more effica

cious in preserving milk than either alone , and that 35 grains of

this mixture are required to preserve a gallon of milk .

Detection of BoricAcid or Borax— The TurmericTest— Evaporate 100 c . c . of the milk , which has been made alkaline with caustic

soda (0-

5 gramme) , to dryness ; i ncinerate . Take up a port ion of

the ash i n water, arid the remainder in weak HCl . Add to each

port ion a few drops of freshly prepared turmeric solution , and

evaporate to dryness . When boric acid o r borax is present , the

residue assum es a brownish- pink colour , which changes to’

dark

green on the addition of a solution of sodium bicarbonate . I f

the watery extract gives no reaction , whilst the acid extract reacts

strongly, it may be concluded that borax is present ; i f the two

reactions are of equal intensity , boric acid has been added ; and

if the react ion produced by the acid extract is stronger than that

produced by the watery extract , it i s probable t hat ' a mixture of

the two i s present .

I f the ash be moistened with dilute HZSO4 , m ethylated

'

spirit

added'

,and the mixture thoroughly stirred and set on fire , a green

border will appear on the flame when boric acid is present .

Estimation of Boric Acid.— The following method is recom

mended by R . T . Thompson:To 100 c . c . milk add 2 grammes

causti c soda and evaporate to dryness in a platinum dish . Char

the residue thoroughly, and heat with 20 c . c . water . Add HCl drop

by drOp till all but carbon is dissolved . Transfer to a 100 c . c .

flask , and add 05 gramme dry CaClz. Run in a ‘

few drops of

phenolphthalein , and then a 10 per cent . solution of caustic sodat ill a permanent pink colour is perceptible, and finally 25~c . c . lime

water . The phosphoric acid is all precipitated as calcium phos

PRACTICAL SAN ITARY SCIEN CE

is oxidized , producing an intermediate oxidation product , whichthen reacts with the protein . He found that the ammonium com

pound of diformaldehyde- peroxide - hydrate ,

an oxidation product intermedi ate between formaldehyde and formicacid , reacts with proteins and pure sulphuric acid , producing the

characteristic colour . This is a general reaction for proteins ,and depends on the presence o f tryptophane (indol - amino - propionic

acid) . The intensity of the react ion with different proteins variesdirect ly as the amount of tryptophane present in the protein mole

cule , and bodies destitute o f tryptophane fai l to give the reaction .

Henner’

s Test— To I o c . c . o f milk in a test - tube add 1 drop

ferric chloride solution , and dilute the milk to about 30 c .c . To a

portion of this in another test - tube add concentrated HzSO4 , by

cautiously pouring it down the side of the tube so as to form alayer at the bottom of the milk . A violet - blue ring will be formed

at the j unction of the liquids .

A few c . c . of the milk are curdled by dilute sulphuric acid , and

a little Schiff’

s reagent (a solution of fuchsin decolourized by sul

phurous acid) added to the filtrate in a test - tube, which is corkedand allowed to stand . In a short time a violet - pink colour is

produced in the presence of the aldehyde .

A further qualitative test:B oil I o c . c . o f milk ; add a few drops

25 per cent . HzSO4 ; filter ; to filtrate add 5 c .c . 0 -1 per cent . solution

of phloroglucin and 5 c . c . 5 per cent . NaOH . A rose - pink colour

indicates formalin .

Estimation of Formalin .

— There is no satis factory method of

estimating formalin . An approximate estimation , which must be

made early, as the aldehyde rapidl y disappears , may be carri ed out

by the following m ethod z— Reagents required a normal solution

o f HzSO4 , a few 100 c . c . bottles , with close-fitting rubber stoppers ,

and a boiler,in which they may be immersed to the neck, a solution

o f methyl orange , and an approximately norm al solution of

ammonia . Place in each bottle 25 c . c . of the ammonia solution ,and to half of them add a sample containing 0 °

5 gramme formalde

hyde ..Stopper tight ly , place the bottles in the boiler, fill with

water to the neck , and boil for one hour . Cool slowly, and titrate

with the sulphuric acid , using methyl orange as indicator . The

differences in the readings of the blanks and the samples represent

M ILK 1 77

the ammonia consumed in normal c . c . Each c . c . grammeformaldehyde . Any acid that may be present must be accountedfor .

The following method ori ginally described by Shrewsbury andKnapp is perhaps as satisfactory as anyother:An oxidizing reagentis prepared by adding 0-05 to 0 -1 c . c . pure HNO

6to 100 c .c . con

centrated HCl . Add to 5 c .c . of milk in a test - tube 10 c . c , of the

reagent ; shake vigorously, and place in a water- bath at a temperature of 50

0C ., In about ten minutes the contents of the tube are

cooled to room temperature . A violet colour indicates formalde

hyde , and its intensity indicates the amount .

. The quantitative. estimation is effected by setting half a dozenmilk tubes containing known quantities of formalin at the sametime as the sample, and at the end of the time. allowed for the testselecting the match

,

Salicylic Acid.~— Precipitate . the proteins from 50 to 100 c . c .

of milk . by the addition of mercuric nitrate , and filter . Shake up

the filtrate with half its volume of a mixture of equal parts etherand petroleum ether , and stand aside until the . ether separates out .

Pipette off the ether, and evaporate to dryness in a clean flask .

Dissolve the residue in a few drops of hot water, and add to a

portion of the solution a drop of a I per cent . ferric chloride solution ;in the presence of salicyllc acid a .violet o r purple colour i s produced .

Add to a s econd po rtion of the solution a little bromine water:sali cylic acid produces a curdy , yellowish precipitate . Evaporate

the third portion of the so lution to dryness with strong‘ HNO

3 ,

and take up the residue in a few drops of water. If salicyli c acidbe present , a yellow coloration 1s produced on adding ammonia .

It should bel

bo rne in mind that carboli c acid and o ther hydroxy

benzene derivatives act in a somewhat simi lar manner to sali cylic

acid . The colour reaction with ferric chloride remains in the presenceof alcoho l in the case o f salicyli c acid , but disappears on addition of

alcohol m the case of carboli c acid .

A further test consists in evaporating a part of the etherealextract to dryness, placing a minute portion of the residue in thesubliming cell , and comparing the crystalline sublimate wi th on e

obtained from pure sali cylic acid . The melting- point_of pure

salicylic acid is 155° to 156

°C .


A4quantitat ive estimation may be approximately made by

matching the colour produced by ferric chloride in a standard solut ion containing 0 05 per cent . salicylic acid in 50 per cent . alcohol .

A 1 per cent . iron‘

alum is recommended instead o f ferric chloride .

Definite amounts o f the salicylic acid so lut ion should be addedto a milk filtrate resembling as nearly as possible that of thesample.

BenzoicAcid’

is but'v ery occasionally found in milk . It is detectedas follows:Render alkaline with baryta -water 200 c .c . milk , and

evaporate down to one - fourth . Mix the residue with CaSO4 toform a paste , and dry on the water- bath . Powder , moisten with

dilute H2SO4,

‘

and extract with cold 50 per cent . alcohol . Neutralize

the alcoho li c extract with baryta -water,evaporate to small volume ,

acidulatewith diluteHzSO4 , and extract with ether . On evaporatingthe ether, any benzoic acid wi ll be found sufli gciently pure for testing .

Make a watery solution o f the benzoic acid, and add a little sodium

acetate ; now add a drop or two o f ferric chloride to obtain a reddish

yellow colour.

Hydrog en Peroxide .—H

202 in the presence of organic matter

rapidl y splits into water and oxygen . I f milk to -which it has been

added be examined before i t disappears , it may be detected by

addition of paraphenylene diamine , when a blue colour is produced .

The reaction depends on the presence of an‘

oxidase , which is

destroyed by heat ; hence if the sample has been heated , it wi ll

be necessary to add a little fresh milk . Mi lk free fr0m 'H20

‘

2de

colourizes Schardinger’

s reagent (5 c .c . alcoholic methylene blue ,

5 c . c. formaldehyde/190 c . c . H20) , but milk that has been treated

wi th H202 Buddeized"

) fails to decolourize the reagent; and onlyregains this power aft er bacterial fermentation has taken place .

Sodium Carbonate .—Ash a weighed portion of the mi lk .

"The

ash of 5 grammes normal milk does not contain more alkalinity

than that neutralized by three - tenths of a c . c . of Excess

o f alkalinity over this may be regarded as sodium carbonate .

Mix 10 c . c . of milk with 10 c . c . o f rectified spirit in a t est - tube ;add 2 o r 3 drops rosolic acid solution (rosolic acid ,

"

1 gramme ;alcohol , 25 c . c water to a litre) . A rose - pink colour indicates

sodium carbonate .

A preservative named mystin (a mixture of formaldehyde and


paper which was previously thoroughly washed with ether ; dryfor three hours at and weigh ; dry for a further two hours

and again we1gh ; dryfor another hour and weigh ( last two weightsshould not di ffer by more than a milligramme) . Deduct

gramme for each c . c . o f strontia used , also the weight of the nlterpaper . Result = non - fat solids .

Correction for Alcohol formed from Lactose — Dist il 100

grammes o f the milk and neutralize the distillate with {6 NaOH( litmus indicator) . Redist il the neutralized distillate and calculatethe percentage amount of alcohol from an alcoho l table . The

percentage weight o f alcohol , x %3 percentage o f lactose that hasdisappeared in formation of alcohol .

Correction for Vo latile Acids — Determine the total acidity in10 grammes of the milk by fir NaOH (phenolphthalein indicator) .Weigh another 10 grammes of the sample in a plat inum dish , andadd half the quantity o f{6 NaOH necessary to neutralize . Ev apor

ate to dryness on a water -bath with frequent sti rring ; add 20 c . c .

boiling water and thoroughly detach solids from dish ; now add

fir NaoH t ill neutral . Difference between original acidity andacidity of evaporated port ion = volati le acidity recorded as aceti cacid ; and 60 parts acet ic acid (CH6

COOH) =62 parts original lactoseR ichmond rightly points out that this co rrect ion

is inaccurate —COZ driven off is calculated as acetic acid ; all volatile

acids are not driven off ; there i s a possibility of lactic acid beingvolatile , and it may be converted into a lactose .

Thorpe makes an ammonia correction:2 grammes of milk aremade up to 100 c . c . with ammoniafree distilled water, and filtered

through a carefully washed filter . Ten c . c . of the clear filtrate are

similarly made up to 50 c . c . in a Nessler glass , and the ammonia

estimated by standard ammonium chloride (1c . c .= 0-01 milligramme

NH6) after N essler’

s method .

Ri chmond shows good reasons for regarding the ammonia correct ion as unnecessary .

The total correction (0 -2 to 0 -

3 per cent . additive) is fairly con

stant in properly sealed samples three to six weeks old .

Bacteria in Mi lk.—Micro - organisms enter milk from the udder ,

during milking , and during transit and distribution . It is not

possible to estimate the total number of bacteria in milk . Perhaps

M ILK 1 81

the best count i s that which demonstrates the presence of pollutionby manure:B . coli

,B . enteritidi s sporogenes .

The methods employed in this work differ in no main principle

from those used in connection with water. The utmo st care is

necessary in thecollection of samples . Dilutions are convenientlymade in sterile flasks or bottles by placing 10 c . c . of milk or of aparticul ar dilution in the vessel which already contains 90 c . c . of

sterile distilled water .Estimation of B . Cali — To a series (better to a double series) of

lactose , bile - salt broth t ubes are added respectively— I o , 01 , 00 1 ,

0 001 , 00 001 , 00 0001 ,00 00001 c . c . (and smaller fractions , i f neces

sary, depending on the degree of pollution of the sample . ) Reco rd

i s made of the smallest quantity producing acid and gas in two daysat 37

°C.

B . Enteriticlis Sporogenes .

— Add 1 ,1 -

5 , and 2 c . c . of the sample

to tubes containing 10 c . c . fresh milk recently sterilized . Add

5 , 10, and 20 c . c . to empty sterile tubes . Heat the six tubes for

ten minutes at 80° C. Cool promptly and incubate anaerobicallyfor two days at 37

°C . Look for the characteristic enteritidis

changes .

Pathogenic M i ero-Organi sms B . Tuberculosi s . Centrifugalize

50 or 100 c . c . of the milk . Examine a portion of the sediment

microscopically. Make and fix films on microscopic slides . Whentho roughly

‘

fixed , wash out all fat with a mixture o f equal partsof anhydrous ether and absolute alcohol . Stain by the ZiehlNeelsen method . Use the remainder of the sediment for inoculating

several guinea- pigs subcutaneously on the inner side o f the left

leg . Ev idence of infection may be found at various subsequentdates in enlargement of the po pliteal , inguinal , sublumbar, and

retro - hepatic lymph glands on left side , and in tubercles in the

spleen . Four weeks is an average time for the production of these

appearances. When the milk c ontains large number of B . tuber

culosis they may be found as early as fifteen days after inocul ation ;when few bacilli exist , five to six weeks may be required to give

results . It is well to make smears from the enlarged glands and

stain with Ziehl-Neelsen’

s fluid . Inasmuch as certain non -pathogenic acid- fast bacteria presenting morphological characterssomewhat similar to B . tuberculosis— such as Moller ’

s Timothy


grass bacill i , Rab inow itch’

s butter bacillus , the smegma bacillus ,‘

m ist bazillus , and Johne’s bacillus— produce tubercular lesions in

the guinea - pig somewhat resembling those produced by B . tubercu

los is , i t i s not always safe to rely on inoculation . The diagnosi s

can be established definitely by sowing on glycerin , agar , o r other

media port ions of the pulp of the lymph glands , from which the

smears above mentioned are made . All the non - pathogenic

organisms will form definite growths in two or three days , whereas

B . tuberculosis will ordinari ly require three or four weeks fo r growth .

It is necessary to investigate the cream in all these details , as well

as the sediment .

The Klebs -Lofller B acillus — Sediment and cream are investigatedmo rphologically and culturally . I f organisms resembling the dipht heria baci llus morphologically are found , they must be grown on

blood serum , and their virulence must be tested by animal inoculation .

B . Typhosus .

— This organism is almost as difficult to detect in

milk as in water . Portions of sediment and cream are applied tothose media intended for the differentiation o f B . typhosus , such as

lactose bile salt neutral red agar, follo wed by subculture on Conradi

and Drigalski’

s medium , malachite green agar, etc .

Streptococci — In the milk o f cows suffering from mastitis ,enormous numbers of streptococci are found , and when these areinoculated into the teats of goats , they set up an inflammatoryreact ion . But since they are found in certain numbers in the

milk o r healthy cows collected in the most cleanly manner, it is

difficult , if not impossible, to estimate their significance . All

that can be said at the moment is , that where streptococci

exist in milk in large numbers , the indicat ion is to examine theanimal for mastiti s , ulceration of teats , etc . Streptococci afise

from the teats and milk ducts of the udder, in large quantities frommanure , in smaller quantities from the air, and may be contributed

by filthy .vessels , foul water, etc . and in those cases where they

occur in very large numbers , i f no inflammatory condition of the

udder be found , it may be assumed that their presence is most likelydue to manure . They can be readily demonstrated in the sedimentby making smears and staining with methylene blue .

Q uantitative estimation is effected by inoculat ing glucose neutra l


The fat is best estimated by Adam'

s process , and the proteins byKj

‘

eldahl ’s total organic nitrogen proces s , using the factor 63 8 .

Cream is prepared by centrifugalizing milk, and contains 45 to65 per cent . of fat . Cream is art ificially thickened with gelat in ,

starch paste, condensed milk , and saccharate of lime . Gelatinmay be detected by drying a weighed quantity and washing outthe fat wi th ether . The residue , when dissolved in boiling water ,wi ll contain the gelatin , which sets on cooling . Or mix a weighedquantity o f cream with warm water ; precipitate proteins and fatw ith aceti c acid ; filter ; add to the clear filt rat e a little strong solution of tannin , when , if gelat in be present , a volumino us precipitatefalls out. A control sample of genuine cream sho uld be operatedon in the same way. It wi ll give but a slight precipitat e .

Starch is discovered by the blue colour it form s w ith a solut iono f iodine .

Calcium saccharate i s determined as CaO in the ash . The

dicalcium phosphate , tri calcium phosphate , calcium citrate , andlime united w ith proteins in normal cream , when transformed intoCaO, amount to about 225 per cent . o f the ash .

Cane- sugar in cream is detected by the rich red colour produced

when to I 5 c . c . of cream ,01 gramme o f resorcinol , and 1 c . c . of con

centrated HCl are added , and the mixture raised to the boiling

point .

BUTTER.

Butter is produced from milk or cream by churn ing . The agita

tion causes the fat globules to coalesce to form granul es o f a finespongy nature . When butter is collect ed and worked , it assumes

a more homogeneous appearance .

The mean composition of butter made from ripened cream , accord

ing to Storch , is:Per C en t.

Fat 82 -

97Water 137 8

Proteins 0 -84Milk- sugar 0 -

39Ash 0 -16

Salt 1 -86

The composition of different butters varies considerably .

I f butter be churn ed at a higher temperature than 13° to 18° C.

BUTTER 85

it will contain more water than at medium temperatures . Very

low temperatures and rapid churning produce an article c on tainingtoo much water .

Butter is adulterat ed with various foreign fats , animal and Vegetable, under the name of margarine , which as a rule are littlein ferior in nutritive qualities to the fat of milk . In the pro

duction ofmargarine , an imal and vegetable fats are 'm elted , filteredthrough coarse filters

,and worked up with milk, to look and smell

like pure butter .It is stated that margarine

,as prepared for the market , is not

quite:so dige stible as butter. Whether or not this, be true , it isillegal to . substitute margarine for butter, and the principal obj ect

of a butter analys is is to determine the presence or absence of

foreign fats .The odour and taste of butter are characteristic , and excellent

tests of its purity . By heating it to 25°

C . any unpleasant taste

that it may possess becomes more.apparent .

Adulteration .—F

.oreign fats are the chief item of adulteration .

Colouring matters , especially annatto, are employed . Water isworked into butter for .the purpose of increasing its weight ; but,as the addit ion of water renders butter liable to decomposition, it

is only possible to e scape detection in cases where the butter israpidly disposed of . The addition “of pepsin , rennet, etc t o milk

before churning aims at increasing the yield of butter by'

securing

an increase of contained water .

The Estimation of Water .— At present butter is allowed to

contain 16 per cent . of water . The following two methods readily

determine the amount of water ; the second 18 the more accurate .

I . Weigh out 10 grammes of butter into a smal l platinum or

porcelain basin provided with a piece of glass rod . Heat on a sand

bath or over a small flame,and carefully st ir until al l frothing

ceases . It is necessary to regulate the temperature so that thecurd is not appreciably browned during the heat ing, and that thereis no loss by spirting . The basin with its contents is cooled in a

des1ccator and weighed . The loss of weight represents the waterin 10 grammes .

-2 . Fill a small platinum or porcelain basin with pieces of pumicethat have been recently washed and ign ited . Select portions of

butter from three different regions of the sample (water is not always


equally distributed throughout the mass o f butter) , and place themin a clean , wide -mouthed , stoppered bottle . Melt at as low a temperature . as possible , and shake vigorously unt il the mass is solid .

Place 5 grammes o f this mass in the porcelain basin , and heatin a drying- oven with good draught at 100° C . for an hour. Cool

and weigh . Replace in the oven for a further half-hour , and againcool and weigh . Repeat the heat ing and weighing until a constantw eight is obtained . The difference between the lowest weighingand that of the orig inal butter is taken as water .

Beake r for me lting Bottle beake r w ith funne l Graduated testtube Platinumcrude butte r. fo r filte ring butte ro fa t. for Va le n ta test. bas in .

FIG . 28 .

The following table represents the variat ions of water in Danishbutters '

Pe rce ntage ofWate r .9 to 10I O 1 1

1 1 1 2

1 2 1 3

Average

N umbe r o f Sample s .

Summe r .1

16

136

335

534

51 2

2871 24

39I 3

414 03 per cent .

Winte r.I

8

20

138

43 I

562

447205

9520

314

-

41 per


performed on this solution without any treatment , as butter is freefrom phosphates .Formalin cannot be estimated with any degree of exact itude , as

it enters into combination with the proteins , so that the uncombined formalin alone reacts , and this gives no information as to theamount originally added .

To estimate salicylic acid treat 20 grammes of butter witha solution of sodium bicarbonate several times in a separating

funnel:salicyl ic acid is converted into sodium salicylate .

‘ Acidifythe extract with dilute H

ZSO4 , and extract with ether ; evaporate the

ether,and to the residue add a little mercuric nitrate , forming a

precipitat e nearly in soluble in water . Filter the precipitate off,

and wash it with water . From the washed precipitate liberate freesalicylic acid with dilute H

zSO4 . Redissolve in ether , evaporate ,

and dry residue at 100° C . Extract the residue with petroleum

ether, and add an equal volume of 95 per cent . alcohol . Titratewith fir KOH (phenolphthalein indicator) . [1 c .c . r

N

o KOH0 -0138 gramme salicylic acid ] Processes which depend on theprecipitat ion of prote ins and detect ion of preservat ives in thefil tered liquid are liable to error owing to the great solubility of

sal icylic ac id and benzoic acid in butter - fat . The extract ion of thefat with solvents (ether, alcohol , chloroform , etc . ) frequently gives

rise to troublesome emulsions . To overcome these troubles Monier

Williams has devised a method of detecting small quantities of

benzoic acid, saccharin , and salicylic acid in cream:Acidify100 grammes of cream with I c .c . concentrated phosphoric acid ;heat with constant stirring either in a porcelain dish on gauze over

a Bunsen or on a boiling-water bath in vacuo (temperature shouldnot rise above 1 20°

C . ) until al l water is expelled . At least 95 per

cent . of the salicylic and benzoic acids remain in the fat , and onlythe merest traces escape in the steam . Filter the clear fat througha dry filter . Al low the fat to cool to 60° to 70

°

C. ; shake with50 c .c . of 0 -

5 per cent . sodium bicarbonate previously heated to60

° to 70°

C . ; when separated from the fat filter the alkaline liquidthrough a wet filter ; acidify with 1 c .c . concentrated HCl ; cool , and

extract three times with 15 to 20 c . c . ether . Dry combined etherextract with CaCl

z,and disti l off ether . The residue will have a

distinctly sweet taste i f saccharin be present . Stir the residue on

BUTTER , 189

a water- bath with 1 c .c . strong ammonia ; evaporate to dryness ;add three or four drops of water and a drop of 10 per cent . iron alum

solution on a glass rod . The characteristic purple colour appears in

presence of salicylic acid, and a buff- coloured precipitate in the

presence of benzoic acid . The method is said to detect with certainty in 100 grammes of cream the following quantities of thesepreservatives occurring singly or all together:o ~oo75 per cent .benzo ic acid ; 00 01 per cent . saccharin ; 0-0002 per cent . sali cylic

acid .

Sulphites.—A portion of the watery liquid is distilled with

dilute HCl, and the gas evolved is passed into “a I solution , whichin turn is titrated with sodium thiosulphate . Sixty - four parts of

SO2 are converted into sulphuric acid by 254 parts of I . Or theSO

2gas may be passed into bromine -water, and the Hz

SO4 formed,estimated as BaSO4 . Sixty - four parts 80

2represent 233 5 parts

BaSO4 .

Butter-Fat:Preparation of Fat for Analysis.—A portion

of the sample of butter is placed in a beaker and heated at a tem

perature of 45°

to 48°

C. in an air-oven . In a little time three

layers separate out in the beaker . _The largest, the butter- fat,

containing a few particles of curd in suspension and a few dropsof water underneath the surface film on the top ; a greyish-whitelayer, the curd, near the bottom ; and underneath a small quantityof water . If the sample be genuine butter

,the melted fat is quite

transparent , whereas if mixed with margarine , melted, and re

emulsified , churned at a high temperature, or rancid , it is generallyturbid .

The fat is poured on a dry filter kept at a temperature above the

melting-point of butter, and is now free from the other constituents ,except about 0-1 per cent . ofwater, and a trace of lactic acid . Thesemanipulations are readily carried out by placing the beaker con

taining the melted butter, and a second beaker ( carrying a fun nel

and filter-paper) in which the fat is received, on the top of an air

oven whose inner tempe rature approaches but does not exceed

50°C . After filtration the fat is rapidly cooled so as to prevent

partial solidification,and

_to obtain a homogeneous mass .Butter- fat contains considerable quantities of the glycerides of

the fatty- acid series CnHm + ICOOH, of low molecular -weight .


The lowest and most important is butyric acid . Acids of the oleics eries are also present .

The various foreign fats which are admixed with butter, such asbeef and mutton fats , lard , cottonseed o il, and other vegetableoils

,present several importan t physical and chemical differ

emees .

Physical Properties of Fats 1 . Me lting - Point. —Fats arenot s ingle substances , but mixtures of different glycerides ; the

melting- points are therefore not sharp . The melted fat is drawninto a capillary tube 1 millim etre bore , so as to give a column about1 centim etre in length . Not less than a day should elapse before thetest , as even pure glycerides of fatty acids that are single chemicalent ities melt at a much lower temperature if they have been recentlymelted than that at which they melt if they are kept in the solidstate for some t ime . The capillary is attached by a rubber band

to the stem of a delicate thermometer, reading tenths of a degree , sothat the column of solidified fat is oppos ite the thermometer bulb .

The thermometer and its attached capillary tube are then immersedin water in a test - tube , and the test - tube in turn is immersed in abeaker of water mounted on gauze over a Bunsen burner . The

water in the beaker is heated gradually (rise of temperature not toexceed 05

°

C . per m inute ) , and the exact temperature noted atwhich fusion of the fat occurs:this is the melting-point . The

flam e is removed ,and the temperature noted at which the fat

solidifies:this is the solidifying—point . Butter- fat melts at about33

°

C . Some foreign fats have melting-points lying very near tothat of butter- fat ; moreover, artificial butters are made to melt atthe same temperature as butter, so this test is of little practicalvalue in distingu ishing pure butter from margarine .

2 . Specific Grav ity. On account of the glycerides of lowmolecular weight which it contains , butter - fat has a greater densitythan the fats used to adulterate it . As it is more convenient to

take the specific gravity of a fluid than a solid, and as Skalwe itfound that at , or around, the temperature 38

°

C . there is the greatestdifference between the specific gravities of butter and foreign fats,this temperature is usually adopted for the taking of specific

gravities .Fill the pycnometer with water at 38

°

C. and weigh it . Remove


6 millimetres diameter,is made to act as a stirrer . The determina

tions should not vary by more than 01 °

C .

4 . The Refractive Index:Cleo-Refractometry.— The oleo

refractometer measures the refraction which a ray of l ight undergoes in passing through a layer of butter . I t is found more conv en ient to read the angle of total reflection , as indicated by the

sharp colourless border- line which vertically intersects the scale ofthe instrument between the light and dark sections of the field ofview . A few drops of the butter- fat to be tested are poured warminto the prism of the instrument , and the deviation noted at a .

temperature of 45°

C . Pure butter gives a deviation of about

30° to the left . Certain forms of margarine give deviations much

less— 15° and 20

°— whilst cocoa-nut oil gives over

The butyro refractometer of Zeiss is a modification of the

Abbé refractometer, and gives rapid readings in scale divisionswhich by reference to a table can be read off as refractiv e

indices .

5 . MicroscopicExam ination .—When examined microscopically

butter- fat presents a collection of small round refractile globules ,together with a few larger globules fairly uniform in size and inthe number present in a single field . Margarine presents a mass of

small globules much less distinct in outline and more crowded

together . The larger globules occur in relatively greater numbers,and present much more diversity in size .

Chem ical Methods used in Analysis of Fats:1 . The Acid

Value .—This is represented by the number of milligrammes of

KOH required to neutralize a gramme of the fat . I t is accordinglya measure of the degree of hydrolysis o f the fat which may be due

to rancidity or to ferment action . Five to ten grammes of the fatare dissolved in alcohol and titrated against tenth normal alkali in

presence of phenolphthalein or alkali blue , 66 of Meister, Lucius.and Bri

’

ming .

2 . The Saponification Value is a measur e of the mean molec

ular weight of the fatty acids entering into the composition of a

fat.I t is to be noted that in the titration of fatty acids soaps

are hydrolysed by water, and accordingly react alkaline ; suchhydrolysis is prevented if 40 to 50 per cent . of alcohol be present .

The sapon ification value is given by estimating the number of

BUTTER 193

milligrammes of KOH neutralized in sapon ification o f I gramme of

the fat.

by the total fatty acids that it contains , whether originallycombined with glycerol or other alcohol , or free . Heat 2 grammes

of fat with 25 c .c . of alcoholic potash in a Jena flask (glass that doesnot give off alkali) under a reflux condenser for half an hour . Carryout a blank control with the same volume of alcoholic KOH in asimilar flask lest the titre be altered by COZ or other agency during

heating . When the sapon ification is complete titrate the alkali in

each flask with HCl and phenolphthalein . The difference

between the amounts of acid required by the two flasks gives theam ount of alkali neutralized by the fatty acids ‘ contained in and

liberated during saponification from the amount of fat taken ; from

this the sapon ification value is calculated .

3 . The Hehner Value .—This is the percentage of fatty acids

insoluble in water produced on saponification by a fat .Two or three grammes of the fat are sapon ified with alcoholic

potash . The saponified'

m ass is washed with hot water into a beakeron a steam bath, and acidified with dilute H2

504 . When the

subj acent aqueous layer has become clear , the contents are filtered

through a weighed filter ; it is well to half fill the filter with waterbefore pouring the fatty acids on . The beaker is washed with a

j et of hot water,"

and the acids washed continuously as long as any

acid reaction can“be detected in the washings .

”The filter with its

funnel are'

“ then immersed in cold water, so that the fatty acidsolidify ; the filter is dried and weighed, or when dry it may bextracted -in a Soxhlet apparatus with petroleum ether, the ether

evaporated, and the residue dried and weighed .

The Hebner value of butter is between 86 and 88, of triolein 95 -

7 ,

of lard and most oils about 95.

4 . The Iodine Value .—This value gives the amount of halogen

reckoned as iodine that the unsaturated acids in the fat take up,

expressed as a percentage by weight of the fat . Triolein,for

example , whose molecular weight is 884, takes up 6 atoms of iodin e

(6 x I Z7 = 762) , or 86 2 per cent ; oleic acid has an iodine v alue of

As saturated acids and their glycerides absorb no halogen,the

iodine value is a measure of the amount of unsaturated acids

13


present ..Acids with unsaturated bonds in more than one place

absorb proport ionately more iodine .

Determ ination by the Method of WlJ S.— Prepare a titrated

solution of iodine monochloride , a t itrated solut ion of sodiumthiosulphate , and a I O per cent . solut ion of KI .

The monochloride is obtained thus:Weigh grammes iodine

trichloride into a 300 c .c . flask, pour in 200 c . c . glacial acet icacid, fit the flask with a cork through which passes a CaCl2 tube ;heat on a water—bath til l the contents are dissolved . Weigh

7-2 grammes of iodine , which has been thoroughly pulverized in amortar, into a second flask ; wash out the mortar with glacial aceticacid, and heat this flask as the other . Pour the contents of the two

flasks into a stoppered litre flask . Any undissolved iodine is

fur ther heated with additional acetic acid till al l is dissolved andadded to the litre flask . This flask is then stoppered and allowed

to cool ; when cold , the solution is made up to a litre with acetic acidand titrated next day . The strength of the iodine chloride solution

is likely to alter a little in the first twenty- four hours , but after thatremains fairly constant for some weeks if care has been taken to

exclude al l water from the glacial acetic acid . To do the titration

pipette into an Erlenmeyer flask exactly 20 c .c . of the iodine

chloride solution ; add about 10 c .c . of the KI solution and about

300 c .c . of water . Run in a standard sodium thiosulphate solution

(24 gramme s to a litre standardized by Volhard’s method) , and

finish off with starch solution . From the amount of thiosulphate

used the amoun t of iodine in the measured amount o f Wijs’

s

solution is cal culated .

Estimation of the Iodine Value of the Fat or Fatty Acid .

Weigh into a stoppered flask of 100 to 150 c .c . capacity a quantityof the fat or fatty acid depending on the iodine value o f the Wijs

’

s

solution used (there should be two or three times as much iodinein the Wiis as the fat can absorb) , say 02 to 05 gramme , and

dissolve it in 10 c .c . CC14 ; add, say, 25 c .c . Wijs , stopper and standaside for a couple of hours in the dark . Now pour the contents of

the flask into an Erlenmeyer (half to litre size) ; wash out any traces

of iodine with 10 c .c . of the K1 solution and afterwards withwater ; the bulk of fluid obtained should be about 300 c .c . Lastlyt itrate with thiosulphate and calculate the unabsorbed iodine .


fatty acids in a fat which volatilize in a current o f steam . The

value is expressed by the number of c .c . o f TH

U alkali required toneutralize the volatile fatty acids liberated under certain prescribedconditions from 5 grammes of the fat . In this country the Wollnymodification is used . Most fats and oils in the fresh state containonly traces of volatile acids or their glycerides , and give values less

than one . Cocoa-nut o il gives Reichert-Meissl -Wollny value 5 to8 ; butter a notable exception possessing a value 26 to 32 . Some

porpoise oils are said to reach 60 .

The estimation is a comparative one , and that only whilst the

conditions are accurate ly observed .

Weigh 5 grammes of prepared butter- fat into a flat- bottomed

flask of 300 c .c . capa city, having a neck 7 to 8 centimetres long by2 centimetres wide . Add 2 c .c . NaOH solution prepared by dis

solving 98 per cent . NaOH in an equal weight of water (protectedfrom the action of atmospheric CO2) and 10 c .c . 92 per cent . alcohol .Heat the flask on a boiling bath for fifteen minutes under a refluxcondenser . Remove the condenser, and drive off the alcohol com

pletely by heating further for half an hour . Add 100 c .c . of waterwhich has been boiled (to remove CO2) , and heat til l the soap dis

solves . Add 40 c .c . of normal sulphuric acid and some bits of

pumice or porous clay, and connect the flask with a condenser tube

7 millimetres in diameter, surrounded by a water- j acket 35 cent imetres long by means of a bent tube I5 centimetres long from the

cork of the flask to the bend of the tube , on the middle of which a

bulb , 5 centimetres in diameter , is blown . The flask is heated on

an asbestos board, with an opening in its centre 5 centimetres in

diameter, by a small flame till the insoluble acids are melted . When

fusion is complete the heat is increased , and n o c .c . are distilled in

about thirty minutes into a graduated flask . Shake the distillate

and fil ter off 100 c .c . into a beaker ; add 05 c .c . of a I per cent .solution of phenolphthalein in alcohol , and titrate with {if soda orbaryta . Carry out a blank experiment with the same quantities ofeverything except fat ; the amount o f T

N

U alkali required to neutralize

the distillate should not exceed 02 to 0-

3 c .c . The number of c .c .decinorm al alkali used, less the blank, multiplied by P L gives theReichert-Meissl-Wo llny number.Leffmann and B eam employ 20 c .c . of glycerol instead of the

BUTTER 197

alcohol used byWollny. They heat the fat with glycerol and sodafor eight minutes, when the fluid becomes clear and is allowed tocool to about 80° C. Then 90 c .c . of water at about 80

°C . and

50 c .c . of a 2 -

5 per cent . HgSO4 solution are added , and the process

is fin ished as above .

In this distillation only a part of the volatile acids distils over

[87 per cent . of total volatile acids (according to Richmond) ; 88 percent . butyric, 88 to 100 per cent . caproic, 24 to 25 per cent . capryllic

(according toFive grammes of pure butter- fat give a number never less than

24, margarine never more than 3 .

In order to prevent fraud notmore than I O per cent . of butter- fat

is permitted in margarines , which wil l produce a Reichert-Wollny

number of 4 .

Example .

— In a mixture ofmargarine and butter- fat the ReichertWollny figure is 16 ; find the percentage of butter- fat .

Taking 3 as the highest possible figure for margarines , and 24

as the lowest for butter- fats, 21 (24 3 ) will represent 100 per c ent .

of pure butter - fat .21 16—3 100

I 3 x I OO62 nearly

This sample , therefore , contains 62 per cent . of butter - fat , and

consequently 38 per cent . ofmargarine .

The Polenske Number .— This number represents the volatile

fatty acids insoluble in water . I t is much used in detecting cocoa

nut o il in butter and other fats . I t may be determined with theReichert -Meissl figure in one weighed port ion of the fat .Saponify 5 grammes of prepared fat with 20 grammes of glycerol

and 2 c .c . of a 50 per cent . NaOH solution . This requires aboutfive minutes , and is complete when the liquid is quite clear . While

stil l hot add 90 c . c . of boiled water, atfirst drop by dr0p, to preventfrothing, and shake til l the soap is dissolved . Warm to and

add 50 c .c . dilute HzSO4 (25 c .c . to a litre ) and gramme of granu

lated pumice (grains I millimetre in diameter) , Connect with dis

ti lling apparatus used in the Reichert -Meissl method, and distilover 1 10 c .c . in twenty minutes . Cool the flask by immersion inwater at I5

°

C. Stopper it, and invert four or five t imes . Filter


through a dry filter fitted close to the funnel ( 100 c .c . of the fil trate

may be t itrated for the Reichert -Meissl numbe r) . Wash thematerial on the filter with three 15 c .c . portions of water, each o f

which have washed out the flask and the condenser . Dissolve thefats on the filter with three 15 c .c . portions of neutral 90 per cent .alcohol . T itrate the united alcoholic washings with {if bariumhydrate , using phenolphthalein as indicator . The number of c .c .

used is the Polenske number .Samples of butter possessing Reichert -Meissl figures 25 to 30

will give Polenske numbers of 1 -

5 to 3 .

Samples of cocoa-nut o il of Reichert -Meissl values 6 to 7 w ill

give Polenske figures I 6 to 17 .

Lard and tallow give Reichert and Polenske figures of about

05 each .

Valenta’

s Test. —~Valenta demonstrated the fact that there isa considerable difference in the temperatures at which various fats

dissolve without turbidity in acetic acid .

Weigh out 2 75 grammes of butter- fat into a test - tube ; add

3 c . c . 99-

5 per cent . acetic acid ; insert a thermometer, and gently

heat with vigorous shaking until the mixture becomes transparent .Now cool down gradually, stirring with the thermometer until thefirst trace of opacity makes its appearance , generally as a fine tai lin the fluid at the extremity of the thermometer ’s bulb . This is

the required temperature . The glycerides of the saturated fattyacids are deposited as the acetic acid cools . The temperature

corresponding with pure butter- fats runs from 29°

C . to 39°

C

and that for margarine falls between 94°

C . and 97°

C . A standard

sample of butter may be tested against a weaker acid giving a

temperature of turbidity of, say, 60°

C. Margarine then gives

100°C . or over . This is a very good preliminary test for the

differentiation of pure butters from margarine .

Exam ination under Polarized ,Light.

— A small particle ofbutter is placed on a clean microscopic slide , and a cover-glass

affixed . The slide is placed on the stage of a microscope providedwith crossed nicols , and examined with a coarse obj ective . In

order to shut out light from the upper surface a short black tubeis laid on the slide in such a manner that the obj ective dips into it .When pure butter- fat , which is non - crystalline , is examined, it pre


If saffron be present,the alcoholic extract will be coloured green

by HNOw'

and red by HCl and sugar .Turmeric is detected by evaporating the alcoholic extract to

dryness, and boiling the residue in a few c . c . of dilute boric acid

solution . A strip of filter-paper soaked in the latter and slowly

dried becomes cherry red . Addition of a drop of alkali turns the

red to olive green .

In recent years a number of l iquid fats have been hydrogenatedby the catalytic action of nickel and other catalysts— oleic acid, e .g

becoming stearic acid— C18H3 402+H2

= C18H36OZ. The physical

change from liquid to solid has enabled manufacturers to incorporate

various oils in margarines and butter . Whether such hardened fatsare equally digestible and equally nutritious with the naturalbodies they now chemically represent remains to be seen . Their

appearance has caused considerable trouble to analysts , as manyof the physical and chemical constants have been completely upset .Bacteria in Butter .

— Economic bacteria take part in the conver

sion of cream into butter . In Europe and America much butter is

made from pasteurized cream , to which starters (cultures of

lactic acid bacteria) are added . By this means the process of

butter-making is much better controlled, and results are much

more un iform . British butter contains from to

micro organisms per gramme . The bulk of these are Bacillus acidilactici , B . lactis aerogenes, etc . which keep in check the development

of unfavourable bacteria, such as B . meseutericus, B . fluoresccus ,B . subti lis, etc . , which give origin to evil flavours, bitter taste, and

rancidity .

The principal pathogenic organism found in butter is the B .

tuberculosis. To detect this organism warm a sample of butter to

42°

C . Centrifugalize the liquid, and inoculate guinea-pigs with

the sediment . It is of importance to note that the butter bacillus

of Rabinowitsch and Petri is acid - fast , and morphologically like

the tubercle bacillus ; and, moreover, when in j ected intraperi

toneally mixed with butter , it produces similar lesions in guinea

pigs . I t is, however, readily distinguished from B . tuberculosis by its

rapid growth on glycerine agar and other ordinary media, forming

an abundant dry mass in three or four days .

CHEESE 20 1

CHEESE

Cheese consists, for the most part, of proteins and fat . I t maybe prepared ( 1 ) by adding rennet to milk, whereby the casein clotsand entangles most of the fat ; and (2) by allowing the milk tobecome sour through the formation of lactic acid, or by the addition

of a dilute acid, such as vinegar, when the cheese contains little fat .

The characters of different cheeses depend on the kinds of milk

used, the methods of preparation employed, and the types of

micro -Organism admitted to the original milk or to the cheese

whilst ripening . During the ripening of cheese a partial digestion

of proteins is effected, resulting in the production of the so - called

primary products of digestion— albumoses and peptones . Later ,secondary products of ripening are found— v iz , amido - compounds

and ammonia .

Whether during these changes fat is increased at the expense of

protein , as was once believed, is doubtful . The relative propor

tions of this digestive work carried out respectively by milk enzymes

and by enzymes of added bacteria are unknown . The flavour of a

particular cheese is due to the micro - organisms growing in it during

ripening .

’

The old idea that a particular cheese , such as Stilton ,can be made only in one locality is exploded . Magnificent Stiltons

are now made in Hampshire by the agency of a ‘ cheese mould

carried to that county from Leicester .So ft cheeses, such as Brie and Camembert , are produced by

clotting milk with rennet at temperatures below 30°

C . , and using

little pressure . Hard cheeses , like Stilton, Cheddar, Gorgonzola,and Gruyere , are clotted at higher temperatures— 30

°

to 35°

C.

and submitted to greater pressure . Soft cheeses contain much

water, and therefore fai l to keep long .

The nitrogen of the proteins in cheese exists in a variety of forms .Van Slyke found that the 38 6 per cent . N of an American

cheddar was distributed as fol lows:Water- soluble N paracas ein -mono - lactate paranuclein 0 -14, cas eoses 0 -22,

peptones

0-18, amides 0-

79, and ammonia 0-13 .

A full- cream cheese contains 30 to 35 per cent . butter- fats .

Fi lled cheeses may contain any proportions of foreign fats mixed

with butter- fats .


If the fat is considerably less than the protein,the cheese was

made from skimmed milk .

fat6 37 total N

(generally 1 -25 to In a skimmed -milk cheese this rat io isless than 1 .

The digest ibility of cheese in the stomach is less than that of

meat , on account of its proteins being covered with fat . Cheese

should therefore be well mast icated,or

,better , thoroughly grated

be fore being used . I ts digestion in the small in testine is effectedwithout difficulty . Owing to the small quantity of water con

tained in cheese compared with that in beef, it has a higher nutritivevalue than the latter . The energy derivable from cheese , as

measured by calories , is about three times that of beef . More

over, the fact that the protein of cheese is chiefly casein , and

accordingly purin - free , should highly recommend it as an article

of diet to those who are in any way troubled by uric acid

In a whole -milk cheese the ratio is greater than 1

Percentag e Composition of a Few Soft Cheeses

\Vate r . Pro te ins . Fat. Ash .

50-

9 18 6 27-

4 3-1

50-0 18-

3 276 401

29-

3 277 38

Percentag e Composition of a Few Hard Cheeses

Wate r. Prote ins . Fat Ash

272 36-6 32

-0 4-2

30 4 36-1 28-

7 4-8

28-6 35-6 3 1

-8 4-0

32-0 35

-1 28-1 4-8

The ripening of cheese has been somewhat differently explained

by Freudenreich, Duclaux, and Babcock and Russel l . When the

curd is thrown down by rennet , it carries with it most of the bacteria

of the milk . Freudenreich believes that the lactic acid organisms ,which develop early and rapidly, are the chief factors in the process

of ripening . Duclaux holds that , since the ripening proceeds afterthe lactic acid organisms have considerably dimin ished , the activeagents are enzymes secreted by a variety of organisms , which he


as possible of the ether. Extract with four additional portionsof ether, and collect the whole in a flask . Disti l off the ether andweigh the fat .Proteins — Treat 1 gramme of cheese by the Kj eldahl method .

N x 6 25 = proteins .

Separation and Determ ination of N Compounds (Van Slyke) .Mix 25 grammes of cheese with an equal weight of quartz sand in amortar, and transfer to a flask ; add about 100 c .c . of water at

and keep the temperature at 50° to 55

°for half an hour, shaking

frequently the while Decant the'

liquid through a cotton filter

in to a 500 c .c . graduated flask . Treat the residue with repeated

po rtions of 100 c .c . of water in the same manner until the water

extract amounts to j ust 500 c .c . Employ aliquot parts of this forthe various estimations .Water-Soluble N — Perfor1n the Kj eldahl process on 50 c . c . of thewater extract =2 -

5 grammes of cheese) .

Pam -Nuclein N —To 100 c .c . water extract add 5 c .c . of a 1 per

cent . HCl solution ; stand at 50° to 55

° til l separation is complete , as

shown by a clear supernatant liquid . Filter, wash the precipitate

with water, and determine the N by Kj eldahl .

N as Coagulable Protein— Neutralize the filtrate from the last

determination with dilute KOH ; heat at 100° til l the coagulum , if

any, settles out completely. Filter, wash the precipitate , anddeterm ine the N in it as above .

N as Caseoses .—Treat the filtrate from the preceding with 1 c .c .

of 50 per cent . sulphuric ac id, saturated with ZnSO4 , and warm to

65° to 70

° unt il the caseoses settle out completely. Cool, filter,

wash with saturated ZnSO4 acidified with HzSO4 , and determine the

N in the precipitate .

N as Amides and Peptones .

— Put 100 c . c . of water extract in a

250 c .c . graduated flask, add 1 gramme NaCl and a 12 per cent .solution of tannin til l a drop added to the clear supernatant solutionfails to produce further precipitation ; dilute to the mark, shake ,and pour on a dry filter ; determin e the N in 50 c . c . of the filtrate

N in amido - acid and ammonia compounds . This minus the

amm onia N = amido -N . Peptone N = total N ' in water extract

minus sum of para - nuclein N , coagulable protein N , and N of

caseoses, amides, and ammonia .

CHEESE 205

N as Ammonia — Disti l 100 c .c . of the filtrate from the tannin

salt precipitation into standard acid, and titrate against standard

alkali .N as Para- Casein Lactate .

— Wash the insoluble residue producedin obtaining the water extract with several portions of a 5 per cent .

NaCl solut ion to form a 500 c .c . salt extract ; determine the N in

an al iquot part of this salt extract .Determination of Lactose .

— Bo i125 grammes of finely divided

cheese with two portions of 100 c .c . each water . Pour on filter ,wash residue with hot water, make up the watery extract to 250 c .c

and determine the lactose by the Fehling or PaVy~Fehling method .

Detection of Foreign Fat.

— Submit the prepared fat to the

Reichert -Meissl method .

Detection of Bacillus Tuberculosis.— Rub up portions from

the central parts of the cheese with sterile normal saline until a

good emulsion is obtained . Strain through sterile absorbent cotton ;and inj ect the equivalent of 2 grammes of cheese into each of two

orthree guinea-

p igs .Lard .

— Freshly rendered lard ( internal abdominal fat of pig) cont ains no .free fatty acids . I t is much adulterated with cottonseed

o il and beef stearin . I t has the following constants:Melting-point,

36°

k

to 45°

C . ; iodine absorption, 50 to 65 per cent ; saponificationvalue , 195 to 197 ; Zeiss butyro - refractometer at 40

°

C .=48

-8°

to

specific gravity at 15 5°

C . , 09 31 to 09 32 .

I f the iodine value fall outside the above limits,the lard is adulter

ated, but a normal iodine figure is no guarantee of genuineness, as a

j udicious mixture of cottonseed arachis or other o il, with beef

stearin , will give normal values when tested .

Infants’ Foods.

— The market is flooded with a large number ofproducts of very varying composition . I f the milk preparations

( condensed , dried, and humanized milks) be grouped as a class all

the other foods contain flours in which the starch is altered or

unaltered, or capable of being altered or otherwise during prepara

tion of the food . I t is necessary to determine the presence,nature

,

and amount of unaltered starch, the extent to which the starch is

converted during the preparation of the food according to instruotions on the label, the presence or absence of diastase in active

form , and the nature of the cereal from which the starch is derived.


With the exception offull - cream dried milks and full - cream con

densed milks , it may be fairly stated that practically al l the infants ’

foods advertised are highly deficient in fat , and many deficient inproteins .The only physiologically suitable food for a young mammal is the

milk of its mother or some other animal of the same species .The chemical composition o f a foodstuff is no criterion of its

nutritional value . Due proportion of protein carbohydrate and fatdoes not constitute a correct diet . For example , the proteins ofdifferent milks vary because of the fact that milks have a develop

mental as well as nutritive function:accordingly milks of differentspecies are not interchangeable . I t is known that the milk of

animals whose chief digest ion is gastric (cow, goat , etc .) forms

solid clots of casein , whilst that of animals whose chief digestion is

intestinal (mare , etc . ) does not form solid clots, but soft gelatinous

m asses, which easily traverse the stomach and intestine .

The digest ion of infants is largely intestinal , and human milk is

the only form which in the early days puts no strain on it . I t is

common clinical knowledge that infants in the first months of lifefed on artificial foods containing starch become the subj ects of

scur vy, atrophy, and gastro - intestinal disorders . The process of

digestion is accompanied by the liberation of considerable potential

energy, and in the case of the in fant with little energy to lose the

digestion of an artificial food,containing in addition to a foreign

milk starch only partially converted, there may not be nearlysuffi cient energy to meet the largely in creased call , with the well

known accompan iments o f this failure— grave nutritional dis

turbance , rachitis, scurvy, anaemia, and more than one form of

profound gastro - intestinal fermentation .

Estimation of Starch:1 . Direct Conversion by Acid .

Hemicellulose and all carbohydrates capable of conversion to sugar

are included with starch .

Wash 2 grammes of the finely divided material on a filter withether, using 10 c .c . four or five times ; continue the washing withfirst 100 c . c . 10 per cent . alcohol, and then with . 10 c . c . absolute

alcohol . Now wash off the contents of the filter into a flask with

150 c .c . water and 20 c .c . HCl (specific gravity, 1 Place the

flask on a boiling-water bath under a reflux condenser for two hours .


obtained is subtracted the dextrose already found ; the differencereduced by 5 per cent . (hydration correction ) is the percentage ofcane - sugar .

Fat. —Fat of dried milks . Owing to the inclusion of fat globulesamongst dried proteins the solvent action of ether in the Soxhlet

method may be greatly inhibited. The Werner-Schmidt methodis in this case more suitable .

Proteins.—The N is determined in 0 -

5 gramme of the food byKj eldahl ’s method, and the figure x 62 5 .

Water .— Five grammes are dried on a water-bath (five hours or

longer) to constant weight .

Ash .— Five grammes are burn t at a dull red heat in a muffle .

I f the food burns with difficulty, Hg

SO4may be added, and a correction made by deducting one - tenth of the weight of the ash .

Cellulose (material insoluble in boiling water and not

attacked by diastase) .— To 5 grammes of the food freed fromfat by ether if necessary add 200 c .c . disti lled water, and bring tothe boil . Continue the boiling for half an hour . Add some cold

extract of malt ( 15 to 25 c .c . according to degree of activi ty) , and

digest at 55° to 60° for three or four hours . Filter through a dry

tared filter . Wash the residue repeatedly with water at 60° C. untilfree from all reducing sugar ; then with alcohol and ether . Dry for

several hours on water - oven and weigh . Transfer filter-paper andresidue to a Kj eldahl flask, and determine the protein . Carry out

the procedure in duplicate , but in the second estimation determine

the‘

ash instead of the protein .

The first weight less the protein and ash = cellulose .

Saccharifying Diastase .— Two or three c .c . of a 5 per cent . cold

water extract of the food are allowed to act for an hour at 21 ° on

100 c .c . of a 2 per cent . soluble starch solution . ,At the end of the

hour the action is stopped by the addition of 10 c .c . rN

u NaOH, and

the whole made up to 200 c .c . The amount of maltose present isdetermined by Fehling’s solution . A food may be regarded as

having a diastat ic activity of 100 when 02 c .c . of the 5 per cent.solution produces under these condit ions sufficient maltose

(o ~08 gramme ) to reduce completely 10 c .c . Fehling’s solution .

I f double the amount is required,the diastatic power is -

5o , etc .

CEREALS 9

CEREALS.

The composition of a fewcommon cereals is given in the followingtable

Ce l l ulose . Wate r.2 2 12 -0

3-8 12 32 1 1 1 -0

12 -0 1 18

2 -2 12 -

32 -

9 12 -

3

9-0 10 5

I t will be seen that the proteins vary somewhat in amount inthe different cereals . The fat appears in increased quantities in

those cereals which grow in high lat itudes . The chief carbohydrate

is starch:it forms 65 to 70 per cent . of the whole grain . The

ash averages about 2 per cent . , and is composed principally of lime

and phosphoric acid, thus resembling the ash of animal foodstuffs

much more than that of vegetables . The high percentage of

carbohydrates is an indication that cereals should be mixed with

other foods richer in proteins and fat; this physiological requirement we find almost universally complied with:butter is spreadupon bread, and the mixture eaten with cheese . On the whole,cooked cereals are easily digested and absorbed .

Wheat-FlouP.—Wheat is the most important cereal used in

this country . I t is consumed to the extent of six bushels per head

per annum . The grain of wheat consists of three portions:(1 ) Thebran or outer envelope of cellulose, containing mineral matter,and forming 13 5 per cent . of the grai n ; (2) the endosperm , con

stituting 85 per cent . of the whole , and consisting of nutritive

material for the growth of the embryo ; (3 ) the embryo or youngplant, forming 1 -

5 per cent . of the grain . The bran consists of

an outer layer of fibres of cellulose impregn ated with salts, a middl e

layer of pigm ent cells, and an inner layer of aleurone grains . The

endosperm consists of a delicate reticulum of cellulose, in whosemeshes are found numerous starch granules . The embryo is com

posed of small cells rich in protein and fat .The milled grain known as flour differs in composition ,

according

I 4


to whether the bran or embryo , or both, have been largely removedor. retained . The reduction of bran to a powder by grinding is a

difficult and expensive matter, and as a rule the miller removes it

altogether. In roller -milling, the germ is also removed , in order

to prevent the fat which it contains becoming rancid . Enzym es

present in the germ act upon the starch, converting it into dextrinand sugar, which darken the colour of the bread ; so the germ is

excluded . This rej ection of the bran and germ means the loss ofsome of the most useful constituents of the wheat ; and the recogn ition of this loss has led to a number of patent processes for treat ing

the bran and germ so as to prevent the production of a dark loaf .In the Hovis process

,the fat of the germ is treated with steam ,

with the obj ect of preven ting its becoming rancid . In the Fram e

Food process,the bran is boiled with water under pressure, with

the obj ect of breaking down the cellulose, and extracting the bulkof the nitrogenous and mineral constituents . In Smith’s patent

the germ is part ially cooked by superheated steam , whereby the

ferment is killed which transforms the starch of the flour . Accord

ing to the method adopted in milling, some flours contain more bran

than others, and some more starches and gluten .

Wheat from different countries varies in chemical compo sition .

Ordinary bread is made from a mixture of flours derived fromdifferent wheats, and sometimes such a mixture includes differenttypes ofmilling .

The average composition of wheat -flour is

Water 130

Sugar 07Ash 08

Fat 1 5Protein 1 1 -0

Starch, dextrin , and cellulose 73-0

Physical Characters of Flour .—Flour should be free from acidi ty,

whi te in colour, and smooth when rubbed between the fingers . I t

should be entirely free from fungi and al l other parasites . A yellow

colour denotes age or fermentation . I f flour be kept in a damp

place , an odour is generated by the growth of moulds and various

micro-organisms .

Gluten .—The crude protein of flour known as gluten possesses


reflex condenser is attached ; boil for several hours under a hood:the starch is converted into sugar (dextrose ) . Make the solution

slightly‘

alkaline with NaOH solution , and estimate the dextrose

by Fehling’

s method . The result, multiplied by 09 ,gives the

quantity o f starch in a gramme . Where cellulose is present , the

small amount converted into sugar may be ignored . The micro

scopic appearances of many starch granules are such as to afford

an easy means of recogn ition . I f a mere speck of a particular

flour or powdered starch be placed on a microscopic slide,a drop

ofwater added, and a cover- slip applied, the starch granules can be

thoroughly studied by low and high powers of the microscope .

As in mounting specimens o f bacteria, it should be noted that it

is almost impossible to apply too little of the m aterial'

to the slide .

The student should observe that in most cases characteristic cells

appear, but that many cells may be unrecogn izable , as belonging

to any particular kind of starch . Where starch granules of different

foodstuffs closely resemble each other, it may be quite impossibleto decide whether or not slight admixture has been effected . Onthe other hand, when the granules are dissimilar the slightest

adm ixture is easily detected .

I f an estimation of the amount of the adulteration be required,

a rough average percentage of the foreign granules may be obtained

by counting a number of fields , and this estimation may be checked

by making a mixture containing the true and foreign ingredients

in the proport ions observed ; such mixture should present the

same microscopic appearances as the original . Several trials may

be made in this way before the required match is obtained . The

student should carefully study the microscopic characters of all

starch granules occurring in vegetable foods, and make drawings

of them .

Bleaching of F lour and Flour- Improvers.—With a view to

improving the baking qualities of flour , millers resort to bleaching

and the addition of‘ improvers .’ Ozone , halogens, and nitrogen

peroxide have been used as bleaching agents . N itrogen peroxidealone appear s to give satisfactory results, and is the only bleacher

now used . The gas is produced chemically from nitric acid and

ferrous sulphate , or electrically by the combination of the N and

O of the air by an electrical sparking discharge . The latter is said

CEREALS 2 13

to be the better method in that the degree of bleaching is moreeasily controlled

, and condensation of acid resulting in staining of

the flour less likely to occur . Air charged with nitrogen peroxideand ozone is agitated with the flour in a suitable machine . I t is

stated that the nitrogen peroxide produced by 3 c .c . of nitric oxide

in 3 litres of air will bleach 1 kilogramme of flour .A watery extract of bleached flour reacts to the nitrite test of

Griess . This reaction is not given by ordinary unbleached flour .

When bleached flour is baked, one

- half to two - thirds of the nitrite

disappears, and an increase in n itrates occurs . The whole of the

nitri te may disappear from biscuits .

Efiecls of B leaching — B leaching destroys the yellow colouring

matter dissolved in a thin layer of oil which surrounds the individualgranules of starch ; the iodine value of this o il is lowered . The acidityof flour is

‘

increased . I t is probable that certain amino -groups in

the protein are destroyed .

Improvers used —Water added to the flour in a fine spray ; phos

phates , especially calcium phosphate ; phosphoric acid ; sulphuryl

chloride . It has been experimentally shown that even traces of

nitrites in flour inhibit both proteolytic and amylolytic digest ion .

The introduction of roller-milling made it poss ible to utilize any

variety of wheat since pulverization of the bran is avoided, and

consequently a more complete removal of bran and germ effected .

The germ contains no gliadin nor glutenin (these substances unite

with water to form gluten) ; it contains I O per cent . of albumin ,

5 per cent . of globulin , and 3 per cent . of proteose . I ts nucleatedcells contain a considerable amount of nucleic acid combined withalbumin and globulin . Little organic phosphorus accordingly occursin the endosperm . Wheat contains probably about 2 per cent . of

germ , and as the latter possesses at least 30 per cent . of proteins ,retent ion of the germ raises the protein content of flour by 0 -6 percent .

The greater port ion of the phosphorus in bran can be extractedw ith dilute acid, and it has been shown that the bulk of thi s phosphorus occurs in organic combination as a phospho - organic acid

,

combined with potassium,calcium ,

and magnesium .

Wholemeal or Graham flour is produced by grinding the entirewheat grain ; it should contain the whole of the g erm .


‘

Entire wheat flour or fine meal is obtained by removing a

portion of the bran , and finely grinding the rest ; it contains a

portion o f the germ .

Straight - run flour is the whole of the flour produced in the

roller-mil ] . The percentage composition of bread made from

samples of these flours is as follows:Prote in Ca rbo Wate r.(N X S hjdrate s .

Graham flour 9-

54 46-10 o -29 42

-68Entire 9 32 487 5 40

-

97 0-

77Straight run 9

-63

Experiments have been made on the nutritional values ofdifferent

varieties of flours . Young rats have been fed on‘ standard or

straight run ,

’ and others of the same age on entire .

’

The first lot

throve much better than the second . Again , the same experiment

has been carried out with Graham flour and entire,

’

or white flour,with results in favour of the Graham variety .

In the milling o f rice the cuticle , consisting of pericarp, testa ,and nucellus, is frequently removed . A diet consist ing exclusivelyof such rice produces polyneuritis and other changes , constituting

a disease known as beri -beri . ’ I f the offal (about 10 per cent . of

the grain) be returned to the rice , no beri -beri occurs . Or if theoffal be extracted by 0-

3 per cent . HCl and the extract pre cipitated

by proof spirit,the substances soluble in alcohol ( 16 per cent . of the

grain ) will equally prevent the disease . It is sign ificant that the

precipitate containing 85 per cent . of the phosphorus of the offal is

wholly ineffective in preventing the disease . A good rice should

not contain less than 0-

4 to 0 -

5 per cent . total phosphorus . The

millin g of rice deprives it o f its cutic le , and leaves it with a dull

appearance . To improve its appearance it is polished in hollow

cylinders fitte d with revolving rollers Covered with sheep- skin . In

order t o obtain a high polish talc or ste atite , in the form of a fin e

powder,is added to the rice prior to polishing, and for the most part

as it passes through the mill . Gypsum , kaolin , and gums have bee n

a ls o used for this purpose . The colour of rice is changed from a

c ream to a dead white by the addition of blue pigments (generally

ultramarine ) during milling, and to make it transparent it is treated

with arachis and other oils .


Barley.—These are ( 1 ) large, (2 ) small , (3 ) intermediate in size .

In a very few are there any markings.

FIG . 3 1 .— RY E . x zo o .

FIG. 32 .— R ICE . x zo o .

Rye.—These are very similar to those of barley, except that in

the large granules some show a rayed hilum and cracked edges ;

CEREALS 2 17

the large granules are more generally c ircular and'

flattened than

those of wheat and barley, and somewhat larger .

FIG . 3 3 .

— OAT . x zo o .

" FIG. 34 .- MAIZE:x

2. Rice, Oatmeal , and Maize exhibit small faceted andangular granules destitute of concentric markings . The granul es

2 1 8 PRACTICAL SAN ITARY S CIEN CE

of rice are small , and collect in part into angular masses . Thoseof oatmeal are s lightly larger, and collect into rounded masses .

Fro . 3 5 .—SAGO . >< 2oo .

FrG. 3 6.—TAP100A . xzoo .

Maize granules are much larger and more irregular in shape, and

most of them possess a stellate hilum .


shape— for the most part somewhat rounded at one side and

truncated at the opposite ; the hilum is either stellate or linear .

FIG . 39.

— ARROWROOT . >< 2oo .

Fro . 40 .

— POTATO . x 200 .

Tapioca granules are much smaller, and the hilum is generallyplaced towards the rounded extremity .

CEREALS 2 2 1

4. Pea and Beam—These granules are oval in form , fairlyuniform in size , and possess a central linear hilum and faint con

centric striae . Those of the pea present a central longitudinal

hilum, sometimes exhibiting cross - striation . .The granules of the

bean are somewhat larger and broader, and the cross- striation of

the central hilum is more marked .

Fro . 4 I .—VIBRIO TR ITI CI . x 30 .

FIG. 42 .— BRUCHUS PI S I . FIG . 43 .

— ACARUS FARI NE .

5 . Arrowroot and Potato .— The granules of these starches

are large, pyriform , and marked distinctly with concentric striae.

A circular hilum is found in both, placed at the large extremity

in arrowroot, and at the small in potato .'

The granules oflarrowroot do not swell in a solution of KOH, as do those of the potato .


Parasites found in Wheat and F lour— An imal Tylenchus

tritici (ear cockle ) . —In the infected ears of grain are to be seen the

larvae of a nematode worm ,occurring as a white powder in dark

misshapen grains . Specimens may be mounted directly in

FIG . 44 .

— PEN I C ILLIUM Fro . 45 .— ASPERGILLUS

GLAUCUM . GLAUCUS

Fro . 46.-MUC0R MUCED O . FIG. 4 7 .

— PERONOSPORAA , H ead ; B and C , conjugation ;

D , spore- bearing hyp ha .

Farrant’s solution , or dehydrated and cleared in the ordinarymanner, and mount ed in Canada balsam .

Bruchus pisi and Calandra granaria are beetles (Coleoptera)which infest grain and pulses . The first attacks the pea

,an allied


Peronospora, which caused the Irish potato famine of 1847, first

affects the leaves,then travels down the stem , and finally attacks

the tubers . The spore -bearing hyphae branch and rebranch, and

at the end of a terminal branch a single spore is developed .

Ustilago Segetum (smut ) .— The spores of this par asite are foundas a black powder infesting ill -developed ears of corn , and fall off

when the ear is rubbed . Examined m icrosc0pically, they are seen

to be brown ,spherical , free spores .

FIG. 49 .—T ILLETIA CAR IES (UREDO x 250 .

Tilletia caries (bunt) is another member of the ustilaginae, and

is found in the interior of the grain ; it may escape detection until

the process ofmilling takes place . The spores are brown , spherical

bodies, generally free , and give to the interior of the affected graina sooty appearance and foetid odour. These spores germinate

in the spring, forming a hypha, the promycelium , which bear s

promycelial thread- like spores . The next stage in the life -historyof this organism is the conj ugat ion of contiguous spores . Two

such conj ugated spores bud and form an elongated secondary

CEREALS 25

promycelial spore , which, if it find a suitable host , sends out hypha:and enters the interior of the grain , where a mycelium is developed .

After a time the hyphae swell, become dark in colour, and a differentiation into spores takes place . As these ripen , the mycelial

structure disappears, and leaves the resting spores in the conditionfrom which the cycle commenced .

Puccin ia gramiuis is one of a large number of parasitic species

affecting corn in the manner above described . A spore attachesitself to a grain or stem , and sends hyphae into its substance , from

FIG . 50 .— WHEAT STEM IN FECTED w rrH PUCC IN IA .

which a m ycelium and spores are formed within ; as a result, the

grain ruptures, .and the spores appear on the surface as rust . A

distinctive feature of puccinia is the double spore attached to a

peduncle . It is this form which is found attached to grain or grass

in the autumn , as rust , and which, known by the name teleutospore , remains quiescent during winter . In spring it germinates ,and produces a non - parasitic mycelium . The individual cells of

this mycelium produce filaments , known as gon idiophores, which

in “turn produce spores at their free ends . Distributed by thewind, these latter fall on the leaves of the barberry, where they

15


germinate and form a dense mycelium in the substance of the leaf ,

giving rise to swellings which proj ect o n its under—surface . Spherical

Go t”

Q D \

FIG . 5 1 .—PORTION o r FIG . 50 SLIGHTLY FIG . 52 .

-TELEUTOS PORESMORE H IGHLY MAGN IFI ED .

FIG . 5 3 .

—JEC ID IUM B ERB ERID IS . FIG . 54 .—C ON ID IOSPORES (UREDO

GON IDIA) AND TELEU’

I OSPORE .

structures , termed aecidia, form and develop within themselves

spores which are set free on ruptur e of the wall of the aecidium .

22 8 PRACTICAL SAN ITARY S CIENCE

and the spores escape . Carried by the wind , the spo res alight on

the ovary o f the rye flower and form a mycelium . On the surfaceof this mycelium free spores (gonidia ) develop , and are surrounded

by a V iscid substance , known as honey-dew, which attracts insects ,

FIG . 56 .

—SCLEROT IUM BEARIN G FIG. 5 7 .

—STR0.\1A CONTAIN INGSTROMA

’

I‘

A . x 1 . AS COCARPS . X 75

by which the spores are carried to other flowers , where the process

is repeated . This stage is known as the sphacelia form .

As the rye is developed , the mycelial growth increases to such

FIG . 58.

— AS COCARP CONTA IN IN G FIG . 59 . Ascus CONTA IN IN GAscr. AS COS PORES .

an extent that the young grain is wholly absorbed, the pericarp isno longer able to contain it

,and it proj ects l ike a spur from the

spike . Ult imately it fa lls to the ground . The cycle is repeated inthe following spring .

BREAD 229

The seeds of Lolium lemuleulum , possessing narcotic properties ,may gain access to flour , but rarely produce poisoning .

BREAD

Bread is chiefly made from wheat -flour . A dough is first formed

by mixing the flour with water or other fluid, and a gas , generally

COZ, is passed through it . Carbon dioxide is obtained either by

the action of yeast on sugar, when this gas and alcohol are formed,or through the liberation of the gas from an alkaline bicarbonate

by the action of an organic acid . The dough is sometimes aerated

by charging water with air and mixing this with flour under pressure

in air- tight chambers ; afterwards the pressure is lowered by opening

a trap, when the dough is blown up by the expanding gas, forming

aerated ’ bread . The dough is then cooked in an oven at a tem

perature of 200-

205°

C .

Composition of White BreadWaterProteinsFatStarch, sugar, dextrinCelluloseAsh

Composition of Whole MealWaterProteinsFatStarch , sugar, dextrinCelluloseAsh

During the cooking a crust is formed, which should neither be

very light nor very dark in colour,and which should crack readi ly

on breaking . The shining appearance of crust is due to the for

mation of dextrin“

, and its flavour and dark colour to the productionof caramel. Two - thirds of the volume of a good loaf is gas . Greatwhiteness in a lo af, although much desired by the public, is byn o

means essential from a nutritive point of V iew, as a very white loaf

possesses a maximum of starch and a minimum of protein .


Comparative Composition of Crust and Crumb °

C rust. C rumb .Water 44 45In soluble protein 73 0 5

-

92Soluble prote in 5

-

70 0 -

75Dextrin and sugar 3 79Starch 62-

58 435 5Fat 1 -18 0 70Ash 1 -21 08 4

By these figures it is seen that there is a much larger prop ortion

of solids, and also more soluble proteins and carbohydrates , in the

crust than in the crumb . The crumb should be elastic in con

sistence , should have a sweet, nutty flavour , and be of a uniform

whi teness throughout . As bread grows old, it becomes hard, and

it has long been known that reheating softens it . The real explanation of the staling of bread does not seem to be known . B ibra

holds that in fresh bread there is free water present , which, as

staleness supervenes, un ites with starch or gluten , and that re

heating sets this water free . He states that the freshness will

not return if the bread has lost 30 per cent . of its water . Othershold that the stale condition is produced by the shrinkage which

takes place in the fibres forming the walls of the pores . The water

vapour formed by the second heating drives these fibres apart again .

I t should be noted that dur ing the baking of bread a large pro

portion o f the fat is lost, amounting to as much as 7 per cent . insome instances

,that the proteins are diminished from 1 to 2 per

cent and the carbohydrates from 3 to 4 per cent . Some of the

starch is converted into soluble starch and dextrin to the extentof 8 per cent .The estimation ofWater and Mineral Matter in bread is per

form ed as in the case of flour . Twenty grammes of the crumb

make a convenient quantity with which to work .

The Ash is generally greater in weight than that of the fl0ur used,owing to the sodium chloride , baking-powder, etc added . Any

excess of ash above 3 per cent . is generally regarded as due to salts

added in order to improve the colour .

Silica is estimated by treating the ash with strong HCl and hot

distilled water in a platinum dish, then filtering through a Swedish

fil ter- paper,carefully washing the platinum dish with further boil

2 3 2 PRACTICAL SAN ITARY SCIEN CE

ign ite , and weigh . The residue is now dissolved in strong HCl,and diluted to 200 c .c and the iron estimated colorimetrically .

Cenv ert the iron thus found into ferric phosphate by multiplying

by 2 7, and subtract this from the weight of phosphates of iron and

aluminium previously obtained ; deduct also the weight of thefilter ash , and the difference is aluminium phosphate , which m av

be returned as commercial alum (crystall ized ammonium alum ) by

multiplying by 37 .

Various cereal and casein preparations have appeared in recent

years contain ing added Phosphorus Compounds in differentform s— glycerophosphates, lecithins , and lipolins, etc . In order to

measure these added substances it is necessary to estimate thephosphorus . This is e asily e ffected by Neumann ’s method:Prepare 2 litres of Neumann

’s molybdate -nitrate solution ; dis

solve 75 grammes of ammonium molybdate in 500 c . c . ofwater, and

pour this into 500 c .c . HNO3 ; add a litre of 50 per cent . ammonium

nitrate solution .

Prepare mashed filter-paper for pressure filter . Place 30 grammesof minced filter-paper in a litre of water containing 50 c .c . HCI.

Heat on water-bath with shaking for an hour . Filter . Wash with

water repeatedly till all acid disappears . Leave in 2 litres of dis

tilled water from which remove portions to pressure filter as

required .

Decompo se 0 -

5 gramme of the substance with nitric- sulphuric

acid ; add 60 to 100 c .c . of water and molybdate -nitrate solution in

excess until solution remains clear on warming . Filter on pressure

filter (about five minutes required) . Add more molybdate-nitrate

solution till all yellow precipitate is down . Wash the precipitate

with water til l free from acid (but not too long, as acid may separate

out of the precipitate ) . Wash precipitate , pulp, and disc (used for

supporting paper pulp in funnel ) into a beaker ; add about 300 c .c . of

water and excess 7,NaOH, and boil for ten minutes or so until

NH3pas ses off. Titrate back with i}Hz

SO4 . Boil again to get rid

of CO2, and fin ish the titration with a drop or two ofgNaOH.

One molecule P205 56 molecules NaOH .

1 c .c . {3‘ NaOH = 1 -268 milligrammes P205 .

[200 c .c . molybdate -nitrate solution =o -1 gramme P205] .

MEAT 23 3

MEAT

The principal food animals are cattle , sheep, pigs, goats , horses ,the buffalo and reindeer in a few countries , and in Saxony and I talydogs .Inspection of animals before slaughter is necessary for the detec

tion of infectious diseases - anthrax, glanders , rabies , etc .

— and for

the discovery of intoxications in which meat and internal organs are

but slightly altered .

Of the many pathological conditions which affect food an imalsthese are of interest in laboratory work:Infective granulations ;a few diseases produced by invisible organisms ; and animal parasites .

Infective granulations are found ,as tuberculosis, glanders , and

actinomycosis .To determine the extent of tuberculosis in slaughtered animals, it is

necessary to make a methodical inspection of the hung-up carcase

from above downwards . The meat is first examined, and afterwards the lymphatic glands

,which receive the lymph from the

meat, in the following order:( I ) Popliteal, inguinal (superficial anddeep) , pubic , or supramammary lymph- glands

. (2) I liac and retro

perit'

oneal lymph-

glandsf (3 ) The lymph -glands along the sides

of the vertebral column,ribs

,and sternum . (4) Prescapular and

axillary glands . 5) Pharyngeal and submaxillary lymph -glands .

On completion of the examination of the lymphatic glands of , the

carcase,the internal organs with their lymphatic glands are next

examined— Via , the kidneys and renal lymphatics , the spleen , liver,lungs, and the udder in female animals .

Lastly the peritoneum and pleurae are systematically inspected .

Actinomycosis occurs as small or large tumours delimited from the

surrounding tissues by a thick wall of dense connective tissue in the

j aws, tongue , skin of head and neck , and much more rarely in the

lungs , liver, kidneys, udder, and abdominal wall .Sections and smears containing B aci llus tuberculosis are readily

prepared and stained with Ziehl -Neelsen’

s carbol - fuchsin , and

counterstained with methylene blue .

Glanders must be distinguished from bovine farcy,not trans

missible to m an , and produced by a fungus of the genus Discomyces .

The ass is more susceptible to glanders than any other animal .


I f a little“discharge from the nose be rubbed into a few scarifications

on the skin of the forehead,an oedematous swelling rapidly appears

,

fellowed by ulceration along the lines of the scratches ; the temperature quickly rises to 40

°

C. or 41°

C . The neighbouring glandsswell, a discharge from the nose appears , and the an imal diesin a few days . The chocolate - coloured gr owth of the glanders

bacillus (B . ma llet) on potato is characteristic . MicroscopicallyB . mallet is a small straight rod (3 to 5 a) , with rounded ends . I t isnon -motile, non - sporing, and Gram -negative .

Sect ions and smears conta in ing the filaments of actinomyces bovis

stain well by Gram ’s method and by carbol - fuchsin . The micro

scopic appearances in both cases are unmistakable . Some difficulty

may be experienced in isolating the parasite from pus in artificial

culture, as the pyogenic organisms overrun the media before theactinomyces has had time to start . Spread pus containing the

yellow granules on a couple of gelatin plates , and incubate at 22°

C.

for two days . Most of the grains will be surrounded by colonies ofcontamin ating organ isms , but a few will be found here and theredi screte and isolated ; pick these offwith a stout platinum wire, and

inoculate three or four coagu lated serum slopes , and incubate at

37°

C . In five or six days (note time as compared with a possible

case of tubercle ) colonies of actinomyces begin to grow . Sown in

glycerin broth,hemispherical colonies appear in the same time (five

to six days) , as large as a small pea, and fall to the bottom , leaving

the medium clear .On glycerin -agar growth occurs in two days, which later becomes

yellowish -white, dry, and wrinkled .

On potato in six to seven days small colourless colonies appear,which quickly become grey , yellow, and finally wrinkled and edged

with black .

The invi sible organisms, or so - called filtrable viruses, producing

diseased condit ions in food animals, are those of pleuro-pneum onia,foot - and-mouth disease

,rinderpest , horse - sickness , swine - fever, cow

pox,sheep -

pox,and bird- plague . Prior to 1898 laboratory methods

failed utterly to throw any light on the causative agents operatingin these diseases . In that year Nocard and Roux devised a new

method of investigation .

In pleuro -pneumonia the essential lesion is the distension of the


albuminous matter . Several animals should be inoculated with alarge volume of the filtrate .

Foot - and -mouth disease infects cattle,sheep

,goats, and pigs ,

and is’

transmissible to m an . Aphthous lymph loses its infectivitywhen kept for five to six weeks . Leffler , by mixing such old lymph

with fresh lymph , attenuated by heating for five minutes at 60° C

has been able to produce immunity in oxen .

B ird - plague virus has been grown by Marchoux on defibrinated

fowl blood spread on glucose - peptone - agar, and incubated at 37°

C.

Growth occurs in the zone of blood adj oining the surface o f the agar.

Animal Parasites in Meat.-Three groups of animal parasites

may be recogn ized:I . Parasites not transmissible to man . I I . Para

sites which may be transmitted to man by eating meat . I I I . Parasites not immediately harmful

,but which may become so after a

preliminary change of host .

I . Parasites not transm issible to Man 1 . The Hair

Follicle M ite in the Skin of Hogs (Demodex phylloides suis) . - It isfrom 0 -2 to 02 5 millimetre long, and produces small swellings of

the hair - follicles,greyish-yellow in colour

,and containing disinte

grated epithelial cells and dermal o il.2 . Dipterous Larvw.

— Larva of warble fly (fi strus bovis) , 28 x 15millimetres, found in subcutis , causes considerable loss to cattleraisers through deterioration of flesh and skins . I t is found in theoe sophagus from July to September, in the spinal canal from Sep

tember to January , in the subcutis and skin from January to May.

Other larvae are the Gastrophi lus equi and G. nasali s .

3 . Numerous Worms which appear in Organs of Food An imals .

(a) All tapeworms except Tcenia echinococcus of the dog, such as

M oniezia expansa found in lambs, Drepan ido taen ia lanceolata and

D . setigera in geese , Davainea tetragona in young fowls, Ta nia

coenurus, T. marginata ,and T . serrata, in the dog . (b) Larval stages

of all tapeworms, except Cysticercus bovis, C . cellulosae, ,and Echino

coccus polym orphus, such as Ta nia coenurus (Ccenurus cerebralis) ,which causes the disease known as gid in sheep, and Cysticercus

tenuicollis ( larva of T. marginata) found in sheep, pigs , and cattle .

(c) Flukes (Trematodes ) , such as Distoma hepaticum and D . lanceola

tum, found in the liver of the sheep . These flat organisms measure

as much as 25 x 13 millimetres . They are covered with scale - like

MEAT 37

spines ou the integument, which irritate the bile -ducts where they are

located,and cause the thickening of these vessels so characteristic o f

the condition . They may wander from the liver to the lungs . Theirembryonic stages are passed in a free condition in molluscs , mostly

water- snails . Apart from the catarrh and cirrhotic condition of

bile-ducts produced by these parasites,haemorrhages occur, and

the health of the affected animals may be seriously damaged .

(d) Round-worms (Nematodes ) , with single exception of Trichinaspiralis, such as Ascarus, Eustrongylus , Filaria (Schneider

’s group

Polymyaria) , Oxyuris , Strongylus (Schneider’s Meromyaria) , Tri

china spiralis, Trichocephalus, Anguillula (Schneider’s Holomyaria) .

I I . Parasites which may be transm itted to Man by eating

Meat.— 1 . The B eef bladder worm (Cysticercus bovi s) , which is the

larval form of Ta n ia saginata of man , known also as T . medio

canellata,consists of a somewhat elongated, rou

'

ndish bladder located

in the interfibrillar connective tissue of the striated musculature ,and occasionally in lungs, liver, and brain . The grey transparentbladder consists of a connective - tissue capsule produced by reaction

in surrounding tissues, and of the parasite . The latter consists of a

scolex and caudal bladder filled with fluid ; the scolex possesses four

suckers,but no hooks . The size of the cysticercus varies from that

of a pinhead to that of a small pea .

2 . The Pork bladder worm (Cysticercus cellulosa ) is the larvalstage of Tania solium . In macroscopic appearances and location

between muscle fibres it closely resembles C . bovis . For the rest,the

cyst is more transparent , so that the scolex when inv aginated intothe caudal bladder appears more clearly . The scolex has twentytwo to twenty- eight hooks in a double circle ; the hooks are of

compressed shape , stout at the base and with slightly curved points .The cysticerci prefer the lumbar and abdominal muscles , pillars of

the diaphragm , intercostal and masticatory muscles .

3 . Trichina Spiralis .

— Hilton investigated calcified trichinae in1832 . Zenker discovered trichinosis in Dresden in 1860 . Afteringestion of trichinous meat, sexually mature trichinae develop in

the intestines of certain mammals ; the parasite is set free from itscapsule by the gastric j uice . Males and females copulate

,and the

females deposit enormous numbers of embryos . Leuchart assumed

that the’

embryos bore their way out of the intestine into the peri


toneal and thoracic cavit ies , and ultimately reach the muscles .Heitzmann argues that this migration cannot possibly take place inthe few days that elapse between the swallowing of infected meat

and the appearance of embryos in the muscles,and that the embryos

are conveyed by the blood - stream , and caught as emboli in the

capillaries . Arrived in the muscles,a capsule is form ed which in due

course becomes calcified . The frequent occurrence of the parasitein rats is explained by the presence of the rat in abattoirs

,knackers ’

yards , etc . Degenerat ion of trichinae in their capsules frequently

takes place . The muscles most likely to contain parasites are those

of the tongue and larynx, and the pillars of the diaphragm .

Rhabditides ( larvae of strongylidae) may be mistaken for

trichinae .

II I . Parasites not immediately Harmful to Man, butwhich

may become so after a Pre lim inary Chang e of Host1 . Echinococci .

- (a ) Ta n ia echinococcus resides as a parasite in the

small intestine of the dog , and is the asexual stage of a tapeworm

with three to four segments . I t is 2 to 6 m illirn etres long by 0 -

3 to

05 millim etre wide . I t possesses a protruding rostellum with

twenty- eight to fifty hooks . The last proglottid is 2 millimetres

long, and contains matur e eggs .

The echinococci occur in two chief forms— (a ) E . un ilocularis and

(b) E . multilocularis . E . un i locularis forms simple cysts surrounded

by connective tissue ; in some cases daughter cysts are developedfrom the mother cysts, in other cases not .E . multilocularis forms daughter cysts by constrict ion from a

central mother cyst , which in turn are furn ished with the samereproduct ive power . The daughter cysts do not remain in the

mother cyst or inside the organic membrane formed about it , butafter constriction become separated from the mother cyst by connectiv e t issue . Accordingly

,the vesicles attain no great size , but

he in the connective t issue like the epithelia of an acinous gland.

The hooks of the multilocular form are somewhat larger than those

of the unilocular .The interm ediate host is man .

The E . unilocularis occurs in the liver, lungs, and spleen, of theox, sheep, and pig, and less often In the heart, kidneys, lymph

glands, muscles , and marrow cavities of bones.


FIG . 60 .—H EAD o r CYSTICERCUs . x 20 .

FIG . 6 I .—T }EN IA SOLIUM

There is a widespread feeling in this country, not by any meansfounded upon knowledge , that the carcase of an animal which has

MEA r 24 1

FIG . 62 .

—TRI CH INA SPIRALI s . x 1 00 .

FIG . 63 .—H EAD o r D I STOMA H EPATI CUM .

died of any disease should not be used as food . In certain cases

this is obviously correct, but in others there is no evidence to showthat the edible parts are in any way deteriorated as food materials .

16

242 PRACTI CAL N ] TARY S CIEN CE

Flesh containing infective parasites,and flesh which is in a

state of putrefaction,including high game

,should be rigorously

excluded from human consumption .

Good fresh meat possesse s certain well - recogn ised characters whichare easy of detection . I t is firm and somewhat elastic to the touch ,

pointing to the fact that rigor mort is is well developed . I t is dryon section, of a clear red colour and acid reaction . A section through

the whole thickness of a j oin t presents a uniform appearance . The

odour of fresh meat may be obtained by running a clean wooden

FIG. 64 .

— AS CARUs LUMBRI COIDES .

skewer down to the bone , and withdrawing and smelling it . The

fat is firm , and not too yellow in colour . Old animals and those fedon oil- cakes exhibit fat of a deep yellow colour . The bone -marrow

is bright red , and coagulates within twenty- four hours .

The lymphatic glands are of normal size , colour, and consistence .

The ash contains a normal quantity of phosphoric acid and s alts

of potash .

When cooked,meat should not lose more than 30 per cent . of

its weight,and when dried on a water- bath to constant weight it

should not lose more than 75 per cent .


Preservatives in Meat— Boric Acid.—A portion of finely

divided meat mechanically freed from fat is warmed with wateracidulated with HCl. The extract is tested with turmeric . Q uantitativ e estimation is made from the same extract as under milk .

Salicylic Acid.

—A portion of meat freed from fat as above isslightly acidified and shaken up with ether ; the ether extract is

evaporated to dryness , and the residue tested in aqueous solutionwith ferric chloride . A violet colour indicates salicylic acid .

Fornzaldehyde .

— This preservative may be used as a solution , and

as a gas in meat - safes and the holds of vessels carrying chilled meats .

Inside safes is placed a receptacle carrying past illes of polymerizedformaldehyde— paraformaldehyde or trioxymethylene— which is

heated until the paraformaldehyde is depolymerized and simplealdehyde vapour is given off. The meat is left in contact withthe vapour for twenty minutes or more . In the holds o f vesselsformalin is evaporated in the presence of the quarters of dressed

meat in the proportion of 10 ounces to cubic feet of space .

Formaldehyde penetrates the substance of the meat , especially areasnot covered by fat

,to distances extending from 5 to 20 millim etres .

The proteins and amino - acids of meat unite with formaldehydeto form methylene - imino compounds

,as demonstrated by Schiff .

The reaction is reversible, and only proceeds to completion in thepresence of excess of formaldehyde:

CIifNHfz

’COSH H '

CHO =CH2:N '

CHz

'

COOH HzO.

m i ne -aceticaCI

Amino - acids composed of basic and acid groups have an ampho

teric react ion ; when treated with H‘CHO they become acid, and

the amoun t of l iberated acid can be readily determined by titrationwith standard alkali:hence the amount of formaldehyde which

enters into the react ion can be determ ined .

The colour reactions by which formaldehyde can be detected inmilk are not applicable to meat, inasmuch as meat gives a violetcolour when heated with HCl in the absence of formaldehyde

( format ion of haem atoporphyrin from Hb) .

Schryver uses the following test:To 10 c .c . of the water in whicha port ion ofmeat has been heated for fiv e minutes in a boiling waterbath, add 2 c .c . of a 1 per cent . phenylhydrazine hydrochloride

MEA T 245

solution . Cool and filter through cotton -wool . Add I c .c . o f 5 percent . potassium ferricyanide solution and 4 c .c . of concentrated HCl .A brilliant fuchsin - like colour is formed

,which in a few minutes

reaches its maximum and lasts for several hours . (The ferricyanide

o xidizes the aldehyde condensation product to a body which is aweak base , which forms a scarlet hydrochloride . On dilution withwater this body hydroly’

ses , forming a base which can be extractedw ith ether to form a yellow solution . If to this last concentrated

HCl'

be added, the base passes back into aqueous solution in the

form of the scarlet hydrochloride . )In those cases in which the formaldehyde amounts to about

1 in parts of meat, I o grammes ofminced meat are used with10 c .c . of water . Where the concentration reaches I part inm eat , 10 grammes of meat are heated with 100 c .c . of water and

20 c .c . of the phenylhydrazine hydrochloride solution . After filter

ing and cooling , 1 2 c .c . of the filtrate (as above )'

are mixed with 1 c . c .

o f the ferricyanide and 4 c .c . HCl .

By comparing the colour obtained with carefully preparedstandards

,the amount of formaldehyde in any sample of meat can

be determined (see Appendix ) .

Bacterial Food-Poisoning (cf. L .G.B . Food Reports , No .

Three groups of bacteria appear to take part in outbreaks of foodpoisoning— v iz the Gartner group of bacilli ; B acillus coli , B . proteus,

etc . ; and B . botulinus .

The Gartner group (B . enteritidi s, B . suipestifer ,'B . paratyphosus B ,

e tc. ) has been found responsible for many outbreaks of poisoningthrough eating pork

,pork pies

,pork sausages , brawn , meat and

minced and baked meat,tinned tongue , tinned salmon , veal pies,

milk, etc .

The B . coli group has been found in milk, meat pies , t inned meat ,etc. B . proteus and other putrefactive bacteria are occasionallyfound in cases of poisoning by sausages , chilled meat, etc .B . botulinus (studied by Van Erm engem ) is occasionally respon

sible for cases of sausage -poison ing .

An experimental investigation in the human subj ect on the

influence of boric acid and borax On food , by Dr . Harvey W . Wiley,

United States Department of Agriculture , was published in 1904 ,

as Bulletin No . 84 ,

~part 1 , Bureau of Chemistry , Washington ; and


a further similar investigation on the influence of salicylic acid and

salicylates was published in 1906, as part 2 of the same bulletin .

Wiley ’

s findings on the influence o f boric acid and borax were

critically reviewed by Professor Oscar Liebreich ; an English translation of Liebre ich

’

s report , dated 1906, is published by J . and A

Churchill .

ALCOHOLIC BEVERAGES

The alcohols may be regarded as oxygen derivatives

of the paraffins . They are colourless and neutral substances possessing neither alkaline nor acid reaction . Those with few carbon

atoms are liquid ; the higher members of the series are solid .

Methyl , ethyl , and propyl alcohols are miscible with water ; butylalcohol dissolves in 12 parts , amyl alcohol from fusel - oil requires

39 parts of water . The relative proportion of oxygen determ ines

the solubility in water ; as oxygen decreases with increasing

molecular weight , the physical characters of the paraffin corre

spondingly predominate . Alcohols resemble water in certain

reactions,in others caustic alkalies . They ,

like water,liberate

one atom of H when treated with sodium , and retain as a substitute

one atom o f the latter . The action of P, B r, etc on alcoholsresults in compounds similar in structure to those formed from

water:2H2

O Na2

2HONa H2.

2CH4O(methy1alcohol ) Na2

2CHJONa H2.

HzO PCl5 2HCl POCls

.

CH40 PCl5 CH3C1+HCl POCl3

.

3H20 PBr

3 3HBr H3P03 .

3CH4O PB r3 3CH3

B r H3PO

3.

The similarity in constitution between alcohols and caust i c alkalies is seen by the following reactions :

NaOH HC1=NaCl H20 .

CH4O HC1= CH3C1+H20 .

NaOH H2804 NaHSO4 H20 .

CH4O HZSO4 CH3HSO4 E ZO

It follows , then , that the graphic formula of an alcohol may beconstructed in the same manner as that for water and caustic soda:


The primary alcohols on oxidation lose two atoms of hydrogen

and form aldehydes:the latter , on continued oxidation ,take up

one atom of oxygen , and are converted into acids .

Ethyl alcohol yields acetaldehyde,and then acetic acid:

CH, CH

8

IH— C— O —H O =H— C= O H

zO .

H— C =O+ O HO— C= O .

The secondary alcohols yield up two atoms of hydrogen in the

first stage to form ketones . Further oxidation forms acids containing fewer carbon atoms than the ketones .

The tertiary alcohols decompose on oxidation , forming ketones ,or acids containing fewer carbon atoms than the alcohol . The

alcohols are found as constituents of many natural products,such

as fats , oils , waxes , etc . They are prepared mainly by fermenta

tion . Ethyl , propyl, butyl , and amyl alcohols are all produced in

this way . Methyl alcohol is obtained by the distillation of wood

and by the destructive distillation of the by-products of the beetsugar industry . Commercial methyl alcohol contains acetone .

When yeast i s added to a solution of grape - sugar o r cane - sugar,

the liquid froths and appears to boil ; the sugar is broken up into

ethyl alcohol and carbon dioxide . Pasteur described this as the

result of life without oxygen , the yeast cells being able in the

absence of free oxygen to use combined oxygen liberated in the

decomposition of the sugar or other substance . Many explanations

of the phenomenon were offered by observers in a controversywhich has lasted for many years .

In 1896 Buchner discovered accidentally that yeast - j ui ce ( freefrom cells) , to which sugar had been added in order to prevent

putrefaction,fermented the sugar ; on heating the j ui ce to 50

°C.

its power of fermentation was destroyed . He concluded that the

production o f alcoholi c fermentation does not require so compli

cated an apparatus as the yeast cell , and that fermentation was

effected by a dissolved substance in the cell to which he gave the

ALCOHOLIC BEVERAGES 249

name of zymase . Yeast - j uice contains a powerful trypti c

enzyme . Zymase when it has acted for some time disappears ,and Buchner concluded that it was destroyed by the endotrypsin .

When a mixture o f alcohol and ether is added to juice , a precipitate

is formed which can be dried to an amorphous powder (zymin ) of

high fermentative activity .

The action of living yeast appears to follow the same law as that

o f most enzymes —v iz. ,the enzyme unites with the fermentable

material (substrate or zym olyte ) , forming a compound whi ch only

slowly decomposes,so that it remains in existence for a perceptible

interval of time . The rate of fermentation depends on the rate o f

decomposition of this compound , and hence varies with its con

centration .

It has been shown by Harden that the addition of a soluble

phosphate to a fermenting mixture of a hexo'se with yeast - j ui ce o r

zymin causes the production of an equivalent quantity of carbon

dioxide and alcohol , which fact , it is concluded, indicates that a

definite chemical reaction occurs in which sugar and phosphate

are concerned . An equation can be constructed embodying two

molecules of sugar in action in which carbon dioxide and alcohol

are equal in weight to half the sugar used,and hexosepho sphate

and water to the other half:

2 (3,,H1206 2PO4HR 2CO2 2C2HGO 2H2

0 C6H10

04 (PO4R2)2.

The main difference between fermentation by yeast - j ui ce and by

the living cell appears to consist in the rate of decomposition of the

hexosephosphate . A comparison of living yeast , zymin , and yeastj ui ce , shows that these form an ascending series with respect totheir response to phosphate . Using fructose as the zym olyte

yeast does not respond to phosphate at all,the rate of fermentation

by zymin is doubled and that by yeast - j uice increased twenty toforty times . It may be that the balance of enzymes in the livingcell i s such that the supply of phosphate is maintained at the

o ptimum , and a further supply , consequently ,does not alter the

rate of fermentation .

Although al cohol is the princ1pal constituent by which such

beverages affect the nutrition of the body,it must not be forgotten

that in many cases ethers, aldehydes,and other by- products of

250 PRAC TICAL SAN ITARY S CIEN CE

fermentation , are likewise found . Al cohol to the extent of 1 percent . seems to be favourable to a digesting mixture in the stomach ;10 per cent . slightly retards gastri c digest ion ,

and 20 per cent .

arrests it. Pancreatic digestion is much more sensit ive to alcohol ;but as digestion is not only a chem i cal process , but greatly in

fluenced by the movements of the stomach and other factors differing widely in different individuals

,it is not surprising to find that

alcohol has very different effects in its relation to individual cases .

It is admitted on all hands that it quickens the act ivity of stomachmovements and secretions . I f the retarding influence of alcohol

on the chemical part of digestion be weighed against it s quickeninginfluence on the flow of gastri c j uice and on gastri c peristalsis, the

balance is in favour of its use as a digestive stimulant . In certain

conditions o fdisease these properties are greatly enhanced . Alcohol,unlike water, i s freely absorbed by the mucous membrane of the

stomach , and requires no digest ion . It passes into the blood at

once . Not only i s it rapidly absorbed itself , but it assists the

absorption o f other bodies . Whilst it passes from the stomach

into the blood, water passes from the blood into the stomach ;the endosmotic equivalent of alcohol i s 4-2,

which means that , for

every gramme of alcohol passing through an animal membrane inone direction , 42 grammes ofwater pass in the opposite .

Al coholi c beverages are all in a broad sense saccharine products ,the result of the fermentation of sugar . In fruits sugar exists in

the j uice, which on exposure to the air ferments:C6H12

06 =2CO2 2C2H60 .

In grain a preliminary fermentation takes place— starch is con

verted into sugar:

2C6H1005 +H O CGHM O5 C

6H1206.

( starch ) ( dextri n ) ( dextrose )

(dextr i n ) ( dextrose)

Beer .

In making beer , barley is steeped in water and spread in layers a

few inches deep on floors , where a temperature favourable to germination is maintained . Diastase i s formed in the grain . When

germ ination has proceeded sufficiently, the grain is dried on a kiln,

25 2 PRACTICAL SAN ITARY S CIENCE

with a few drops of strong solution of iodine in KI ; add solution of

NaOH till the mixture is nearly decolourized . On standing aprecipitate o f iodoform ( star - shaped o r hexagonal tablet crystals )form swhere alcohol is present to the extent of o r per cent .

Acetone , lacti c acid ,and certain aldehydes and ketones, give this

reaction , but not pure methyl alcohol , amyl alcohol , o r aceti cacid .

FIG. 66.

— ESTIMAT ION or ALCOHOL .

Estimation of Alcoho l .— Expel free CO2 by shaking in a flaskor separator funnel and drawing the still liquid away from the

froth .

Into a 250 to 400 c . c . flask pour 100 c . c . beer ; add some tanni c

acid to prevent frothing ; dilute to about 150 c . c . with H20 and

distil . All the alcohol will come over in the first 75 c . c . distillate

t.e. ,three - fourths the original measured volume .

’

In the case of

liquors high in alcohol , it i s better to distil over about 100 c . c .

Make up the dist illate to the volume of the liquor originally taken


and shake well . Take the specific gravity in a pycnometer. Refer

to the alcohol table , and read off the percentage of alcohol by

volume or by weight .Tabarie

’

s Method.— Find the specific gravity o f the beer .

Evaporate 100 c.c . on a water - bath to one - fourth the volume .

Make up to the original volume with distilled water, and find the

specific gravity of the dealcoholized fluid . Add 1 to the original

specific gravity,and from the sum subtract the second specific

gravity . The difference is the specific gravity corresponding to

the alcohol in the liquor . Suppose the specific gravity of the

sample to be 19 899, and that of the dealcoholized sample

Then I ~9899 10 099 09 800 16-24 per cent . alcohol by volume .

Acidity.-The total acidity is usually expressed in terms of

lactic acid . Measure 20 c . c . beer and free it from CO2 by raising

it to the boiling-point . Cool , and titrate with 1156 NaOH , using

litmus as indicator . I c .c . 11

h NaOH 0 009 gramme lacti c acid .

The Fixed Acid expressed as Lactic.— Evaporate 20 c .c . beer to

one - fourth its volume , dilute with water to original volume ; tit rate

with {T

U NaOH as before .

Volatile Acid expressed as Acetic.— Distil 100 c .c . beer nearly

to dryness . Should the residue in the retort be still acid, add some

water and continue the distillation to dryness . Now titrate the

distillate with “fir NaOH, each cubic centimetre of which 00 06

gramm e°

acetic acid . The normal acidity of beer is due to COZ,acetic , lacti c, malic, and other organic acids , and should not exceed

in 100 c .c . that neutralized by 30 c .c . 1373 NaOH .

The Malt Extract. —To estimate this item with any degree

o f accuracy , a small quantity must be operated on . Take 5 c .c . or

5 grammes in a large platinum dish so that a thin film is formed on

the bottom . Dry for two or three hours on the water- bath,and

finish the drying in an air-bath at a temperature somewhat above

100°C.

Bitters.— The bitter of hops is readily soluble in ether ; the bitters

of quassia , aloes, and hop substitutes, are insoluble in ether ; whilst

many bitters that might be employed are soluble in ether,the

absence of a bitter taste from the ether extract demonstrates theabsence of hops . In performing the test

,evaporate the beer to the

consistence of a syrup before extracting with ether . Further, lead


acetate completely precipitates the bitter material of heps , butleaves behind some o f the bitters o f hop substitutes

, which may

be recognized on concentrating the filtrate .

Aloes .

— Dry 200 c . c . beer and treat the residue with ammonia .

Filter, cool, and treat the filtrate with HCl. Collect the resin on afil ter . This i s insoluble in cold water, ether, petroleum ether, and

chloroform , but soluble in alcohol . It has a characteristi c odour

which identifies it .Gentia n .

— Treat the acid residue with chloroform in the cold:nocolour i s produced ; warm , and a carm ine - red colour appears . A

small quantity of the red solution mixed with a drop or two offerri c chloride solution changes to a greenish -brown .

Qua ssia .

— Quassiin in acid solution is soluble in chloroform ,and

,

when mixed with a little alcoholi c solution of ferri c chloride,gives

a mahogany - brown coloration .

Preservatives in Been — B oric acid and salicylic acid aredetected in the same manner as described under milk, concentrating

the beer if necessary to one -fifth or one - tenth o f the bulk . Sac

charin is detected by acidulating a portion with H2SO4 , shaking

with a mixture of equal volumes of ether and petroleum spirit ,evaporating down with a little NaOH solution , and carefully

heating for a short t ime to about 250°

C. Sali cyli c acid i s formed ,

and this is tested for in the ordinary way .

Sulphurous Aci d.

—To 25 grammes sample in a 200 c . c . flask add

25 c. c . N -KOH . Shake and set aside for twenty minutes . Add

10 c.c. 25 per cent . HzSO4 and a little boiled starch solution .

Titrate rapidly with gi

giodine t ill a blue colour i s produced . One c . c .

of the iodine solution = o -ooo64 gramme SOz. Sulphurous acid is

used to regulate the fermentation and to produce a flavour ofage .

S odium Chlori de .

— Where common salt has been added, an

allowance not exceeding 50 grains per gallon must be made for the

amount of this compound present in the water, malt , and hops

used . Ash a suitable quantity of beer, say 100 c .c . ; exhaust the

ash with water ; titrate the solution with T’

% AgNOa, using neutralpotassium chromate as indicator .

Arsenic— In Lancashire in 1900 an outbreak of arsenical poisoningoccurred

,in which arsenic amounting to r

’

ograin per gallon was fre


quantities of a standard solution o f As containing from o °oo5 to

milligramme As ,O3 . Such standard solution i s prepared bydissolving 0 -1 gramme pure in a little pure NaOH solut ion ,

acidifv ing with pure HgSO, , and making up to 100 c .c . with water.

Ten c . c . o f the latter fluid is further made up to I litre . One c.c

milligramme AS QO3 .

Reinsch’

s Test.

—Acidify 100 c .c . beer with 1 c .c . HCl ( free fromarsenic ) ; evaporate to less than half the bulk . Set up two beakers

on gauze over Bunsen burners (the second to act as a control ) . In

the first place the prepared beer, and in the second an equal volumeo f water . To each add 5 c .c . concentrated pure HCl and a strip

o f bright pure copper- foil 10 millimetres by 5 millimetres . Heatfor an hour

,replacing from time to time the water lost by evapora

t ion . If a deposit forms on the copper , remove it , and wash verycarefully with water, alcohol , and ether . Place in a subliming

tube and heat over a low flame . The crystals are for the mostpart regular octahedra

,with perhaps a mixture of rectangular

prisms .

Clarke has made this test quantitative:Dissolve the arsenic fromthe Cu slip in dilute aqueous solution of potash and H

2OZ in the

cold . Then boil , and filter off any CuO. Concentrate the filtrate

to a small bulk and wash into a distilling flask with strong arsen ic

free HCl ; add some ferrous chloride ; fit the flask with a safety tube

and connect with a small worm condenser . Distil down twice withpure strong HCl. Pass H S into the dist illate . A precipitate will

form if more than 0 -1 milligramme be present ; i f less than this

quantity,a yellow colour . As little as 00 01 milligramme arsenic

sulphide gives a faint yellow colour, which may be matched by a

series of standard colours produced under the same conditions .

"

Wine .

In making wine the j uice of the grape is left in open vats where

its sugar undergoes spontaneous fermentation . The bloom which

covers the outside of the grape contains the necessary yeast , and the

natural acidity o f the juice, or must , excludes foreign organisms .

See description of Marsh—Berzelius process , Analyst, February , 1902, xxv ii . ,

48, 2 10.


The relative porportions o f protein and sugar influence the

character of the wine , as yeast (Saccharomyces ellipsoi deus) lives

upon the protein,and splits the sugar, forming alcohol and other

products . If yeast grow in little sugar and much protein , it can

maintain its existence until all the sugar is changed ; such a wine

is said to be dry and acid, like hock . Conversely , if there be muchsugar and little protein , the growth of yeast comes to an end before

all the sugar is used,and that left behind produces a sweet wine .

Intermediate proportions of sugar and proteins produce corre

sponding results . It may be noted , though , that , no matter whatthe proportions of protein and sugar, fermentation cannot proceed

after 16 volumes per cent . of alcohol have appeared in the liquid ;this is why a natural wine can never contain more than this proportion of alcohol . Sherry and port are fortified wines— that is ,containing, as they do,more than 16 per cent . of alcohol , they

have the difference added to them . Claret and hock are natural

wines . The quality of wine depends on the species of yeast used,

the .v ariety of grape , the soil and climatic conditions of growth of

the grape,and the mode of its cultivation . The colour of red

wines is produced by a pigment (cenocyanin ) residing in the skins

of the grapes,which is .turned red by the acids present ; As

alcohol is produced, it dissolves out this pigment , and so coloursthe distillate . Wine , when placed in casks , undergoes im portant

changes:water evaporates more quickly through the woodworkthan does the alcohol , and so the alcohol becomes concentrated .

Further , some oxidation of the tannic acid takes place ; this causes

white wines to be somewhat darker in colour, and red wines lighter,through the carrying down of some of their pigments by oxidized

tannic acid . Frequently a small amount of yeast enters the cask,

and continues the fermentation,thereby increasing the quantity

of alcohol . With the lapse of time , some of the alcohol is oxidized

into acetic acid, and certain compound ethers are formed . Wine

in bottles adds to its contained ethers , although its alcoholic

strength rarely, if ever, Increases . It is an error to suppose thatvery o ld wine contains most alcohol:slow oxidation in the case ofwines

,as in all other o rganic compounds , produces degeneration .

It is more than probable that no wine improves in quality aftera period of ten to fifteen years .


Fermentation progresses most rapidly at a temperature between

5° and 30

°C but finer bouquet is produced by slower fermenta

tion , and accordingly must is fermented in open vats in cool cellars

at 5° to 15

°C . t ill it settles out comparatively clear, care being

taken to avoid acetic fermentation . When the first or active

ferm entation is complete , the wine is drawn off into casks,where

it undergoes a second slow fermentation , with deposit of potassium

bitartrate and development of the characteristic flavour . The

wine is somet imes Clarified with gelatin , and sometim es pasteurized ,

before the final bottling or casking . Volatile ethers predominatein natural wines , fixed ethers in fortified . Sparkling wines , as

distinguished from still,are highly charged with CO either pro

duced naturally by after- fermentation of added sugar (champagne ) ,or artificially by carbonating , as in the case o f soda -water .Port wine is rich in tannin , and to certain inferior wines this

astringent,together with alum and catechu , is added . Port con

tains a large amount of extracts , which give it a full body ,and old

port a large proportion of ethers , of which (unlike sherry) thefixed ethers predominate over the volatile .

Sherr ies , as imported into this country , are all fortified and

plastered,and contain from 15 to 25 per cent . of alcohol by weight .

Old sherry contains a large proportion of vo latile ethers,and to

this property much of its value as a stimulant must be attributed .

Champagne is produced from black grapes , and depends for its

Character very largely upon the quality of the grapes of a particular

vintage . The expressed juice , after sedimentation for twelve hours ,i s drawn off and fermented ; it is then bottled and allowed to undergo

secondary fermentation for a couple of years , during which tim e

much CO2is produced , and a deposit . To the wine , which is up

till now sour,cane - sugar

,which has been dissolved in o ld cham

pagne,i s added in varying quantities . Dry champagnes which

find their way to England contain little sugar— not more than 1 or

2 per cent whilst sweet cham pagnes may contain 10 to 15 per cent .

Claret is a deep red wine , somewhat acid and astringent ; it con

tains little sugar,but considerable quantities of volatile ethers .

Its content of alcohol varies from 8 to 12 per cent . by volume .

Hock is a white wine containing little sugar , 9 to 12 per cent . by

volume alcohol,and is mildly acid .

260 PRACTICAL SAN I TARY SCIEN CE

Get rid o f CO2by shaking . Heat about 20 c .c . to boiling , and

titrate with rN

o NaOH ( in white wines and cider use phenolphthalein as indicator) . One c .c . {

i

v NaOH = 0 -0067 gramme malic

acid , or 00 075 gramme tartaric acid . This is the total acidity .

Volati le Acids.—Place 50 c . c . with a little tannin in a distilling

flask connected with a condenser . Connect a second distilling

flask containing 250 c .c . water with the first by glass tube passing

almost to the bottom . Heat both to boil ing ; then lower the flame

under the distilling flask and pass steam through the wine until

200 c .c . distillate come over . Titrate the distillate with TN

U NaOH

( indicator phenolphthalein ) . One c .c . TN

T;NaOH= o -oo6 gramme

acetic acid .

Ethers .—Ethers are produced in wines by the chemical action

which takes place between the acids and alcohols . Volatile ethers

are obtained from volatile acids , such as acetic , and these , especially

acetic ether, predominate in natural wines . Fixed ethers are

derived from fixed acids , such as tartaric , and are found in forti

fied wines ; they impart to wine its bouquet . ( Enanthic ether

I part in wine imparts the vinous smell and taste to all

wines in common .

Extract — Dry I O grammes to constant weight in a platinumdish ; a small am ount of glycerin may be lost .

Ash .— Ignite the dried residue at a low temperature and weigh .

Most natural Wines contain I part ash to 10 parts extract .

Sug’

ars .— Th

'

e chief sugar of wine is laevulose , of which a

natural wine should not contain more than 0-

5 per cent . Fortified

wines may contain from 2 to 25 per cent . Extractives found in

wineconsist of gums and various carbohydrates, and contribute tothe taste and so - called body of the wine . Reducing sugars are

determined by Fehling ’s method .

Potassium Sulphate.— Acidify I OO c .c . of the wine with HCl ;

boil and add excess BaClz. Filter, wash well, dry , ignite , weigh as

BaSO4 ; calculate the equivalent K2504 . More than 00 6 grammeindicates plastering .

ALCOHOLIC BEVERAGES 26 1

Spirits .

Spirits.—Whisky

,brandy, rum , gin , etc .

Whisky.—Whisky is made from malt or malt and grain , and

distilled in pot - stills or patent - stills . For many years superior

claims were made for the pot - still article , but these claims have

been destroyed by the report of the recent Royal Commission .

In 1905 a London magisterial investigation decided that patentstill spirit alone is not whisky , and that whisky cannot be made

from maize ; the above report upsets this View .

The pot - still in its simplest form is a pot with a long neck overwhich the distilled alcohol passes when the wash or fermented

mash of grain is boiled . Usually two distillations are carried out

in producing Scotch whisky .

The patent - still is an arrangement of pipes and chambers through ,

which steam is passed continuously as the wash disti ls . This is a

cheaper process capable of a much greater output .

The Commission concluded that it would be no advantage t o pro

hibit the use of foreign barley, and it would be tooarbitrary to say

that Scotch whisky should be made from malt alone , and Iri sh from

a mixture . Maize affects the flavour, but there is no valid reason

for excluding it . Patent - still whiskies are less vari ed than pot- still ,but the same effects are produced by both kinds if taken in the

same quantity and in the same strength .

Pot- still distillers admit the need of blending with patent - still

whisky, unless their own spirit can be matured longer ; patent - still

tones down the pungent taste of the other . Cheap blends containas little as I O per cent . of pot - still . As whiskies used in England

are usually blends,and as the patent - still is adapted for economical

and larger production , and as there is no evidence that the form

o f still has any relation to the Wholesomeness of the spirit , the

Commission could not recommend that the term whisky " should

be restri ct ed to the pot- still variety .

Brandy is determined by the report as a potable spirit made from

fermented grape- j uice'

and from no other materials . British

brandy is defined as a compounded spirit prepared by a rectifieror compounder by redistilling duty-paid spirits made from grain

with flav ouring ingredients, or by adding flav ouring materials to

26 3 PRACTICAL SAN ITAR Y S CIENCE

such .spirits ; the nature of the flav ouring materials is not disclosed .

True ~brandy is distilled wine , and was originally procured froma rich Cognac district in France . Its quality varies with thecharacter of the grapes used , the best grapes yielding grande

champagne , a genuine liqueur brandy . It is to be feared thatlittle of the brandy sold in this country is so derived . B randy

contains, beside ethyl alcohol , volatile ethers in large amount ,an important distinction from whisky . Its percentage of alcoholis about the same as that o fwhisky .

Alcohol — Estimation by distillation as under B eer .

Metallic Impurities.

— Pb , Cu , etc . Detection and estimation asunder Water .

Fusel-Oi1. —Fusel - o il is the most important impurity of spirit .

It is more injurious than ordinary alcohol,and should not be

permitted to exceed o z per cent . ( I ) Shake 20 c .c . of the spirit

with 2 c . c . dilute KOH . Evaporate on water-bath to z or 3 c .c .

Cool and add 5 c .c . strong sulphuric acid . The odours of valerianicand butyric acids will be detected if fusel - oil be present . (2 ) Distil

off four-fifths of the sample , and extract the residue with ether ;allow the extract to evaporate spontaneously , and treat what is

left with HzSO4 and sodium acetate:the odour of pear is emitted .

(3 ) Evaporate 50 c .c . slowly over a steam - bath ; carefully smellthe remainder for traces of fusel - o il . (4) Decolourize a portion of

the sample with animal charcoal and add a few drops each of hydro

chloric acid and colourless aniline - o il . In the presence of fusel - o il

a rose tint is produced in the aniline - o il .

[Tests for methylated Spirit:( 1 ) Odour ; (2 ) a weak solutionof sodium nitroprusside ( 1 per cent . ) and ammonia , added to a

mixture containing methylated spirit,give a red colour within

ten or fifteen minutes ]Estimation— M arquardtM ethod — To I OO c . c . spirit add 20 c .c .

NaOH , and saponify by allowing to stand overnight , or by boilingfor an hour under a reflux condenser . Distil 90 c .c . ; add 25 c .c .

water, and distil an additional 25 c .c . Saturate the distillate with

NaCl and add saturated NaCl solution till specific gravity is 1 -1 .

Extract the salt solution four times with CCl4 (recently purified by

boiling with sulphuric acid and potassium bichromate , and distilling )


them up with water and pipette off. Oxidize I c .c . of the oily

liquid by heating in a glass tube at 90°C . for eight or ten hours

with 2 parts NaCl, 3 part s Cu (NO3 )2, and 100 parts clean sand .

Ex haust with warm alcohol , filter, and make up to 100 c .c . with

alcohol . In the case of pure spirits the liquid is red , but in the

presence of I per cent . methyl alcohol it is violet . Dilute 5 c .c . of

the coloured liquid to 100 c .c . with water, and dilute 5 c . c . of this

again to 400 c .c . Heat the liquid in a porcelain dish with some

pure white merino wool (free from sulphur) for half an hour . I fthe spirits be pure the wool will remain white

,but if methylated

the fibre will become violet . A quantitative estimation can be

made by comparing the tint with a set of standards containing

known percentages ofmethylic alcohol .

Rum is prepared from molasses, a by- product in the m anufac

ture of sugar , but the best varieties are obtain ed by fermenting thejuice of the sugar- cane . One by-product— ethyl butyrate— confers

upon it its characteristi c flavour . Like brandy, however, muchof the rum sold in this country is made from silent spirit , flavoured

with characterist ic by- products .

Gin is prepared by distilling and redistilling a mixture of rye and

mal t . In the last distillation j uniper berries , salt , and hops , are

added , and the product is run off into cisterns lined with white

t iles , whereby colouring matters are prevented entering the spirit .

The best gins are disti lled in Holland ; but much o f the gin of

commerce is concocted from silent spirit , resins , and juniper berries .

The term proof- spirit is applied to a mixture of 57 -06 per cent .

by volume of absolute alcohol in water . It has a specific gravity

of 919-8 at 15

°C .

B randy ,whisky

,and rum , may be 25 degrees under proof— that

i s , may contain 75 per cent . of the alcohol found in proof- spirit .Gin may be 35 degrees under proof— that is , may contain 65 percent . of the alcohol found in proof- spirit .

Spirits generally contain 40 to 60 per cent . of alcohol ; wines

8 to I 6 ; beers 5 to

Acidity of Spirits .— Titrate with decinorm al alkali and calculate

as aceti c acid . One c . c . {9 alkali: 0-006 gramme acetic acid .

Esters .—Dilute 250 c .c . of the spirit with 50 c .c . water, and distil

200 c .c . Neutralize 50 c.c . of the distillate with decinorm al'

alkali


(phenolphthalein indicator) ; add fir alkali in considerable excess .

Boil for an hour under a reflux condenser . Cool and titrate with firalkali . The number of cubic centimetres T

N-

G alkali used in the

saponification multiplied by 0'

0088= grammes esters calculated as

ethyl acetate .Furfural.— Prepare a standard furfural solution . Dissolve

I gramme redistilled furfural in 100 c . c . 95 per cent . alcohol .

Dilute I c . c. of this to 100 c .c . with 50 per cent . alcohol . One c .c .

0-0001 gramme furfural . Dilute 20 c .c . of the above distillate to

50 c .c . with 50 per cent . alcohol free from furfural . Add 2 c .c .

colourless anilin and 0-

5 c. c. HCl, specific'

gravity I -125 . Make

standards , from which match the tint .F'urfural is found in pot- still, but not in patent - still , spirit .

Alcohol Table .

Per Ce nt. Per Ce nt. Per Ce nt. Per Cent.Alcoho l (VOL ) . unde r P roof. Alco ho l (VOL) . unde r Proo f.

PRACTICAL S AN ITARY S CIEN CE

Alcoho l Table— conti nued .

Pe r Ce nt. Pe r Ce nt. Pe r Cen t.Alco ho l (VOL) . unde r P roo f. Alcoho l (VOL) .


Tartaric Acid — Mix 20 grammes of juice with 5 grammes KCl ;neutralii e with KOH , and make up to 50 c .c . with water . Add

5 grammes citri c acid , stir the solution ,and stand overnight .

Wash‘

the precipitated acid potassium tartrate with a saturated .

so lution of acid potassium tartrate , and afterwards two or three

times with I 0 per cent . KC] . Titrate hot with fir NaOH ( I c .c .gramme tartaric acid . )

Estimation of Citric Acid— Warrington’

s M ethod.

— Neutralize15 to 20 c .c . o rdinary juice

,o r 3 to 4 c .c . concentrated juice ,

with normal soda,and make up to about 50 c .c . Heat on a

water-bath , and add CaCl2 until slightly in excess of the organic

acids present . Boil for half an hour, filter, and wash the precipitate with hot water . Concentrate the filtrate and washings

to about 15 c .c . and add a drop of am monia,which produces a

further precipitate . Collect this on a small filter with the assist

ance of the previous filtrate ; wash with a small quantity ofhotwater .

Dry both precipitates ; ignite at a low red heat , and titrate the ashwith

TN

U acid ( I c .c . 00 07 gramme H3'Cis O) .

Vineg ar .— Malt vinegar , as distinguished from wood vinegar

( acetic acid and water) , i s made by soaking malt or malt and barley

in successive quantities of hot water until the extraction is complete , fermenting the extract with yeast , and finally pumping the

fermenting mass over wickerwork coated with Mycoderma aceti by

which the alcohol is converted into acetic acid . Other bodies ,such as aldehydes , acetic ether, etc . ,

are form ed at the same time .

Specific Grav ity .- Determine in the usual way ; specific gravity

should be about 1 0 19.

AceticAcid .

—Dilute I o c . c . to 50 c . c . and titrate with {3 NaOH

(phenolphthalein as indicator) . ( I c .c . TN

U NaOH= o -006 gramme

acetic acid . )N itrogen .

— Operate on 25 c .c . by the Kj eldahl pro cess .

Phosphoric'

Acidr —Operate On 25 c .c . by Neumann ’s method .

Sulphuric Acid.—When the ash of vinegar fails to be alkaline ,

min eral acid has been added . Evaporate 50 c .c . of the sample to

dryness with 25 c .c . NaoH , and ignite at lowest possible tem

perature . Add 25 c .c . {‘

U HCl, heat to expel CO2, and filter ; wash

with hot water,and collect washings

,and filtrate . Titrate the

free acid with $6 NaOH and phenolphthalein ( I c .c . TN

G NaOH

gramme H2504 ) .

M US TARD 269

Total S olids — Evaporate 25 c .c . to constant weight . Ignite the

residue at a low temperature to obtain the ash .

A good malt vinegar contains roughly 55 per cent . aceti c acid ,

25 per cent extract , 05 per cent . ash , 00 75 per cent . P205 , 00 75per cent . N ,

and has a specific gravity of I -020 .

Mustard — Mustard i s derived from the seeds of the black and

white mustard plants (Bm ssica nigm and alba ) . A little turmeric

and coal- tar colours are usually added to the ground seeds , and

sometimes foreign starches and ground chillies (small pods of

Cayenne pepper) . These adulterants are all harmless . Starch is

readily detected by the iodine test . Turmeric becomes brownish

red under the action of ammonia . White mustard is recognised

under the m i croscope by the hexagonal or infundibuliform cells

FIG. 67 .— CELLS OF CUTICLE OF MUSTARD.

o f the cuticle , possessing a central ostium occupied by the so - calledmucilage cells .

Mustard o il is a slightly yellow refractive liquid of strong odour .It boils between 148

° and 156°C . , and has a specific gravity varying

between 1 0 20 and P 030. Colour changes to reddish-brown on

exposure to light . Volatile o il of black mustard interacts withammonia to form thiosinamine:

NH3C3H5CNS=

The o il is estimated by extracting with ether in a Soxhlet ’sapparatus . Good samples contain about 30 per cent . o il .

Pepper.— B lack pepper is derived from the unr1pe berries of

Piper nigm m , and white pepper from the ripe fruit . A transverse

section of a black-pepper berry presents an external layer of cells,

somewhat resembling bean starch granules , within these a layer


of elongated cells arranged transversely to the foregoing,next a

reti culumcontaining o il globules , more internally still a layer o fflask - shaped cell s , and finally a central mass of angular cells con

tainingstarch .

Pepper is largely adulterated , but with substances which are

harmless . These are various foreign starches , pahn -nut powder,

ground stones of olives,ground shells of walnuts , and occasionally

chalk , clay ,and brick - dust .

FIG. 68.—BLACK PEPPER.

The ash of black pepper should not exceed 6 5 per centand that of white pepper should not exceed 3 5 per cent . In

mi croscopically examining pepper, it must be remembered that ,unlike mustard

,pepper naturally contains starch .

Sugar .—Glucose (dextrose ) . or grape- sugar, and fructose (laevu

lose ) occur in grapes and other fruits, together with sucrose ( cane

sugar) .

Cane - sugar probably develops first , and afterwards gives originto the other two ; this change is readily produced by hydrolysis

HzO Cl mO11 C

6H1206 (glucose ) C

6H1206 (fructose ) .


red cuprous oxide , and ammoniacal silver solutions form a metallicmirror .

The ~ reaction of glucose and other sugars to excess o f phenylhydrazine in acid solution enabled Fischer to demonstrate the

H OH

c

+H,0g

H OH H OH

c c

H OH H OH

chemistry of the carbohydrates . I f glucose be heated with excess

of phenylhydrazine and acetic acid, the insoluble osazone separates

after some time .

S UGAR 273

Glucose,mannose , and fructose give the same phenylosazone .

Glucose is transformed into the hexahydric alcohol sorbitol byreduction with sodium amalgam ; in like m anner m annose is con

verted into mannitol,and galactose into dulcitol . Glucose is

oxidized to gluconic acid by bromine ; the aldehyde group becomes

carboxyl .Oxidation .by nitric acid transforms glucose into bibasic saccharic

acid .

Glucose is rapidly oxidized in the animal body under normal

conditions to CO2and H

20 ; but when combined with such bodies as

chloral and camphor,the aldehyde end of the

'

glucose molecule

escapes,and oxidation takes place at the other extremity , producing

glucuronic acid,which is excreted in the urine .

The power of removing toxic substances from circulation in

combination with glucose appears to be common to both the animaland vegetable kingdoms . The salts of glucuronic acid in animals

are analogous to the glucosides in vegetables .

Disaccharides consist of two six- carbon atom groups j oined by

an oxygen atom , and are consequently analogous to the simple

glucosides . On hydrolysis they split into their constituent hexoses ,which may be either aldoses o r ketoses . One hexose reduces cupri csalts

,forms an osazone , and displays mutarotation like glucose ; the

other fails in all these respects . Maltose and lactose belong to the

first class .Rubner’s isodynam i c law— Vlz in dietaries , fats and carbo

hydrates are mutually replaceable in definite proportions,the sole

limitation being t hat imposed by the digestive organs —is,in the

light of recent work , only partially true . This method of assessing

the value of a dietary on its calori c value , whilst of admitted use , is

misleading . It takes no account of the chemical form of foodstuffs .It is now certain that in man at least there must be a constant

supply of carbohydrate circulating in the body fluids . Even in

advanced starvation the glucose content of the blood varies butlittle from that of the normal . If fat be largely substituted forcarbohydrate , the output ofN rises , and this rise of N is due to the

demand of the organism for sugar which is extracted from amino

acids in a word , undue katabolism takes place in the mostimportant tissue constituents . This protein breakdown cannot be

18


inhibited by the administration of fat . Again , Of the two stereoisomeri c forms of glucose, one is preferentially metabolized by the

animal organism . It may be fairly stated that o f isomeric synthetic

foodstuffs that form alone i s assimilated and oxidized that occurs in

nature . A limit is thus set to the synthesis of foods .M anufacture of Cane-Sagar .

— The juice o f the cane is extractedby the rollers of the crushing-mills , and is freed from proteins ,acids , etc . , by defecation — coagulation of albumins

,etc . ,

and

neutralization with milk of lime . When the impurities are removed

as a scum, the ju i ce i s subj ected to evaporation and crystallization .

The raw sugar is thus separated from the mother- liquor, o rmolasses .But sugar is prepared by digesting sliced beets with warm water ,

and then clarifying as above .

Sugar is refined by clarifying it with various reagents— lime , clay ,

acid phosphate of calcium , blood , etc . The syrup from which thepurified sugar is crystallized is sold as golden syrup .

’

Sugar is met with in all conditions o f purity

Raw sugars (brown sugar, etc . ) contain from to 5 per cent .

ofmoisture ; refined sugars below 05 per cent .

The ash consists of lime , oxides of K and Na ,alumina , silica ,

and runs from 0-05 to 2 per cent . Sometimes brown sugars contain

sand .

Aniline dyes are employed to colour sugars . Such sam ples will

turn pink on addition ofHCl and a little heat .

The natural colour of sugar is not extracted with alcohol ; i f

the dyed sample be extracted with this reagent in the absolute

form , and - a little wool previously mordanted with alum inium

acetate placed in the solution , the wool will be coloured yellow .

Further, on examination of the crystals with a microscope , the dyewill be found unequally distributed .

B eet - sugar is bleached with 502, or bone black ,and afterwards

dyed with ultramarine .

Cane - sugar (sucrose) i s dextrarotatory, but invert - sugar (the

product of hydrolysis ) is laevorotatory ( fructose is more laev orotatory than dextrose i s dextrorotatory ) .Maltose is produced by the action of diastase on starch . It

crystallizes in small needles , is dextrorotatory , and displays muta

rotation . It reduces Fehling’s solution , forms a phenylo sazone ,

2 76PRACTICAL SAN ITARY S CIEN CE

When a leaf is immersed in a warm 20 per cent . solution of

NaOH ,

mounted on a slide,and the cover- slip pressed down , long

FIG . 69 .

—CUTICLE OF TEA~LEAF. x 200 .

FIG . 70 .

— ID IOBLAS TS I N S ECTION OF FIG. 7 I .

— TEA -LEAF .

TEA - LEAF .

tenacious,branched cells

,term ed idioblasts , are to be seen . These

cells do not occur in any other leaves likely to be mistaken fo r tea .

B lack and green teas differ only in their mode o f preparation .

TEA 277

Composition of an Av erag e Sample of Black Tea

Water 82

TheinTannic acid 164Pectin , cellulose , chlorophyll 4o

~6

Proteins I S°O

Alcoholic extract 7 3Ash 63

Of these constituents,the most important are the alkaloid thein

and tannic acid , for these , with 05 per cent . of volatile oi l , produce

the characteristi c effects of tea .

Indian and Ceylon teas are richer in all three constituents (thein ,

tannin,volatile o il) than China teas ; and green tea is richer in tannic

acid than black ; but the amount of thein is about the same in both .

I f tea be infused for five minutes in the usual manner, about

one - fourth of the weight of the leaf goes into solution . The thein

is so soluble that it passes into solution almost immediately, but the

tannic acid requires.

some tim e to dissolve . There is less tannic

acid after three minutes’ solution than after five , and less after

five than after ten ; after a longer interval there is not very much

change , as practically all the soluble materials have been extracted

in ten minutes ; therefore the less tanni c acid desired , the shortershould be the

ftim e of infusion ; The method of infusion is , from a

health point of view, more important than the character of leafused . First , the water should be of_medium hardness , well aerated ,

and just brought to the boiling point , when tea is infused . If thewater be too hard , the lime and other salts present interfere with

the extraction of some of the constituents of the leaf ; i f, on the

other hand , it be too soft , an unpleasant , bitter material is e x

tracted . Infusion should last for about three minutes,as not only

does prolonged infusion extract too much tannic acid , but it also

dissipates the volatile o il to which the fragrance of tea is largely

due . A further point of import is that too much leaf should notbe infused ; considerably less than the proverbial teaspoonful per

head , when properly infused , is sufficient to produce the most

fragrant and pleasant beverage . The addition of milk to tea ,through the proteins that it contains

, tends ~to precipitate some of

the tannic acid . Sugar adds considerably to its nutrit ive value .


The average proport ions of the three act i ve ingredients in ordinary“

teas in use at the present day are roughly as follows:

2 to 4 per cent .

10 to 1205

Adulteration .

- Adm ixture with foreign leaves , such as elder- leaf ,sloe - leaf , and the leaf of the willow,

has been effected . A low

power microscope readily detects any of these (the leaves mostcommonly employed ) from the tea - leaf

,as none of them possess an

FIG . 72 .

— ELDER-LEAF . FIG . 73 .

— VVI LLOW - LEAF . FIG. 74 .—SLOE- LEAF .

emarginate apex , nor do their systems of venation leave a clear

space within the margin . The employment of infused leaves has

been practised , and it may be sometimes difficult to distinguishcertain prepared leaves from the genuine leaf . Various chemicals

have been used to colour and ‘ face previously infused leaves ,such as turmeric , sulphate of lime , Prussian blue , and black- lead .

Old leaves have been worked up with sand and gum,and re - rolled .

I t may be quite impossible to detect small quantities of such leavesin adulterated samples , since genuine teas vary, much in the relative amounts of their constituents . The ash of tea should fall

between and 6-2 per cent . , and the ash soluble in water should

not fall below 30 per cent . of the total ash . Reference to these "


dry , powder , and carefully extract with chloroform in a Soxhletapparatus . Evaporate the chloroform extract , and boil the residuewith water . Filter . Evaporate the filtrate to dryn ess ; cont inuethe drying at a temperature under 100° C . Weigh , to obtain theamount o f thein in 5 grammes of tea . Thein under the microscope

appears as long , white , silky needles . If the preliminary extractions are not thoroughly perform ed ,

some Of the thein will remainin the t issues of the leaf .A short and rapid method o f detecting thein in tea - leaves is the

following:Take two watch -glasses of the sam e size , and place inone a small quantity Of tea

,and cover with the other . Mount the

pair on a wire gauze over a small Bunsen flame . In five minutes

the upper glass will exhibit numerous drops of moisture ; in tenminutes some fin e needles of thein will be seen ; and in fifteenminutes a thick crop of fully formed needles will have condensedon the watch -glass . Exhausted leaves produce no such cry stals .

I f the watch - glass be floated on cold water, crystallization is has

tened .

Catechu is added to tea to produce a semblance of richness to

the infusion . When present in quantitv ,it may be detected bv

precipitating an infusion Of tea with neutral lead acetate and

filtering . Five c . c . of the filtrate , when mixed with 2 drops of

dilute ferri c chloride solution , assume a green colour, which ulti

mately settles as a darker precipitate .Estimation of Tannin Proctor

’

s M odiflcation of Lowenthal’

s

M etkod.— Ascertain how much perm anganate of potassium is

reduced by tanni c acid,and other readily oxidizable substances

in the infusion . Precipitate the tannin by gelatin ,and once more

determine the amount of permanganate reduced . The difference

represents the quantity of permanganate decomposed by tannin .

Boil 5 grammes powdered tea in 400 c .c . water ; cool , and make

up to 500'

c .c . To 10 c .c . filtered , if necessary , add 25 c .c . indigo

carmine solution (6 grammes indigo and 50 c .c . concentrated H2SO4per litre) , and about 750 c .c . water . Run in from a burette potas

sium permanganate solution (about 1 3 3 grammes per litre ) a littleat a t ime , stirring the while till the colour becomes light green , then

drop by drop till the colour changes to bright yellow or faint pink

at the rim . Let the number of c .c . perm anganate used: a .

TEA 28 1

Mix I OO c .c . of the clear infusion with 50 c .c . gelatin solution(25 grammes gelatin soaked for an hour in saturated NaCl solution ,

heated till dissolved cooled,and made up to a litre) , and I OO c . c .

o f a solution consisting of 975 c . c . saturated NaCl, and 25 c .c . con

centrated HZSO4 ; add I O grammes powdered kaolin , and shake

well in a stoppered flask . When settled , decant the clear fluid on

a filter,and afterwards bring the

‘

precipitate on the filter . To

25 c .c . o f the filtrate , corresponding to 10 c .c . of the original in

fusion , add 25 c . c . indigo carmine solution (6 grammes indigo

carmine and 50 c .c . concentrated HZSO4 per litre ) and 750 c . c . water,and t itrate with permanganate as above .

Let the number of c .c . permanganate used 6.

Now a = perm anganate required to oxidize all oxidizable sub

stances present,and b= quantity of permanganate required to

oxidize substances other than tannin . Therefore the differencea— b= perm anganate required to oxidize the tannin . Titrate the

number of c .c . perm anganate represented by a — 6 against TN

W oxalic

acid . Assuming that 00 63 gramme oxalic acid= o -o_4157 gramme

tannin (gallotannic acid) , the amount of tannin is readily calcu

lated .

Coffee .— Coffee is derived from Cafiea arabica . The bean is

enclosed in an outer layer of fruit like the stone in a cherry ,and

consists of two symmetrical halves faced together, and covered by

a husk . The external pulp is removed by fermentation ,and the

beans are dried in the air ; later, the husk is separated by rolling .

Many varieties o f bean are to be found,the finest of which is

Mocha . The beans must be roasted in order to prepare the

beverage . The composition o f raw and roasted Mocha coffeeb eans is as follows:

Raw . Roasted .

Caffein 1 0 8 0-82Caffeic acids 8-

46 47 4Sugar 9

-

55 0 -

43Alcoholi c extract I 4

-I 4Fats . 12 -60 13 59Legumin , dextrin cellulose 48

-69 600 9MoistureAsh 3

-

74 4-

56

roasting of coffee dissipates a small quantity of caffein andI O per cent . of fat , and produces an o il— caffeol— to which


the aroma o f roasted coffee is due . It precipitates the albuminsand separates some carbon .

Caffein Is almost ident ical chemically with thein ,but whilst thein

is combined with tannin in the form of a tannate,caffein is com

bined with an acid allied to tannin (caffetan ic acid ) , which is notpart i cularly astringent , does not coagulate gelatin ,

does not precipitate alkaloids (quinine , and gives a light -green colorat ion

FIG . 76 .

— COFFEE BERRY .

with Fe2C16 instead of the thick black liquid produced by thein and

tannin .

Thein tannate is not very soluble In cold water , but easily solublein hot . The caffein compound is readily soluble in cold water .

When coffee infusion is saturated with (NH4 )2SO4 a precipitate is

obtained which contains a small proportion o f th4

e total caffein inthe free state ; in tea infusion similarly treated nearly all the theinis precipitated .

The tea compound is precipitated with weak acids , and presumably by the acid Of the gastric j uice , and is accordingly not absorbed

t i ll it reaches the alkaline small intestine . The coffee compound is


seconds and filtered , i s rarely below and averages about

The specific gravity o f a coffee infusion prepared in thesam e manner is never higher than and averages

Other and rarer adulterants , such as ground carrots , turnips , etc . ,

will give infusions of Specific gravities o f and over . (4) Mi cro

scopic examination o f the powder will demonstrate the character

istic dotted and lacteal ducts of chicory ,whereas in coffee portions

of the membrane or testa lining the berry ,and containing the char

acteristicspindle cells , will appear , as also endosperm cells . (5 ) All

foreign bodies added to coffee are devoid o f caffein . (6) I f to a

5 per cent . infusion of pure coffee is added a slight excess of basic

lead acetate , a precipitate falls , leaving a colourless supernatantfluid:the corresponding supern atant fluid in chicory is coloured .

FIG. 78 .

— LACTEAL VESSELS FIG . 79 .

— Do rr ED VESSELSOF CH ICORY . x I OO .

OF CH ICORY . x 100 .

l

When acorns,potatoes

,sago

,etc are mixed with coffee , micro

scopic examinat ion will detect their starch granules . Infusions of

coffee and pure chicory are not blued by iodine . Caramel may be

detected by its shining particles when viewed with a hand lens , asthey stand out in contrast with the dull particles of coffee ; alsoby its ready solubility in water .Various art ificial coffee -beans containing little or no real coffeehave been found at t imes upon the market . Coffee extracts are

deficient in caffein .

Estimati on of Cafiein .— The method described for the estimation

of thein may be used . An alternative method is the following:Moisten I o grammes finely powdered coffee with 2 5 to3 c .c . water ;stand for half an hour . Extract with CHCl3 for three hours in a

Soxhlet . Evaporate the extract . Treat the residue of fat and

COCOA 285

caffein with hot water ; filter through a cotton plug , and wash with

hot water . Make up the filtrate and w ashings to 50 c . c . Pipetteoff40 c .c and extract four times in a separator funnel with CHCla.

Evaporate ; dry the caffein at and weigh . Calculate the

percentage .

Cocoa.— Cocoa is prepared from the seeds of a cucumber- like

fruit— Theobroma cacao . The seeds are separated from the fruit ,heaped together for some days , and allowed to ferment , which

modifies their b itterness and darkens their colour . They are next

roasted , when the symmetrical halves of the seed separate as coco a

nibs on being submitted to pressure in a machine . The nibs may

be sold in this form , or they may be ground between hotrollers .In the latter case the fat is melted , and the products of grinding

are consequently reduced to a fluid . A considerable portion of thefat is removed by pressure

,and the remainder, having been run into

moulds,and thus converted into solid slabs , is once more ground

and sold as a powder . Strictly speaking , cocoa is not soluble in

water ; the Dutch manufacturers add alkalies to it , which saponify

the fat and somewhat soften the fibres of the cocoa .

Composition of Cocoa as Raw Nibs

Fat 50-

44StarchProteins 13 2 0

Various a stringents 6-

7 I

Gum and cellulose“ 8 57Other non - nitrogenous bodies 58 0

Colouring matter 2 -20

Alkaloid 08 4Water 5

-23Ash 2 -

75

The chief alkaloid of cocoa is theobromine (dimethyl -xanthin) ,a body closely related to caffein . In the commercial powder the

50 per cent . of fat is reduced to 30, or under .

Adultemnts .

— Foreign starches,which can be more or less easily

detected by the microscope . Alkalies are frequently added in

considerable quantities for the purpose of increasing the solubil ity

of the cocoa . A determination Of the ash , which in unadulteratedvarieties rarely exceeds 4 per cent will assist in detecting suchadditions .


Chocolate is ground cocoa from which the fat has , or has not,been removed . Sugar, starch ,

and various flav ouring -materials

are added , and the whole melted and thrown into moulds , o r pre

pared for distribution in other ways .

Theobromine may be est imated thus:Remove the fat andcaffein by petroleum spirit

,and dry the extract on the water- bath .

Boil this extract in water for a considerable time . Next extract

the residue not affected by petroleum with chloroform for severalhours in a Soxhlet apparatus . Drive Off the chloroform on a water

bath,and boil the extract several t imes with water . Mix the two

extracts in water,and evaporate to dryness in a platinum dish .

Weigh the residue as theobromine .

288 PRACTICAL SAN ITARY SCIENCE

o f the solvent emploved . Still later Bechold and Ehrlich demon

strated certain relat ions which exist between chemical constitutionand disinfectant act ion , and Bechold published his views on therelations which exist between disinfect ion and the chemistry of thecolloids .

We have known for some years that certain relations exist

between the const itut ion o f chemical substances and their physio

logical action . Ant ipyrin , for example , owes its analgesic properties to the presence of the organic radical methyl (CHa) . The

introduction o f a second methyl group forms a new body po ssessing the same pain - allav ing properties in a greatly increaseddegree .

Desgrez pointed out in 191 1 that non - saturation of the molecule

increases the toxicity of the nitriles,and in a proportion greater as

the saturation is less . The corresponding amides are subj ect tothe same law . The germicidal power of an organi c compound isdirectly proportional to the number and kind of certain radicals

(phenyl , methyl , naphthyl) , or, under certain conditions, ofhalogens

(Cl, B r, I ) , found in the body . The germ i cidal activities of such

radicals differ widely amongst themselves— cg , the group phenyl

(C6H5 ) i s about five times more energet ic against certain bacteriathan methyl (CH3 ) . Again , oxygen combined with carbon and

hydrogen , and even with nitrogen , increases the bacteri cidal power

of the compound . N itrogen combined with one or two atoms of

hydrogen always lowers antiseptic power . The substitution in an

amide group of an antiseptic group (phenyl, naphthyl, etc . ) im

mediately raises the bactericidal powers of the compound . By theaccumulation of phenyl groups large increase in germicidal powers

has been conferred on several compounds . B echold and Ehrlich

found that the introduction Of sulphonic groups , on the other hand ,

lowers germ i cidal power . Scholler and Schrauth have Shown that

the introduction of halogens (Cl and I ) in the benzene nucleus o f

oxymercuriobenzoate of soda notably augm ents the disinfectant

power of this body . But after a certain amount of halogen has

been incorporated , further additions fail to raise it . Bechold and

Ehrlich ,working with a phenyl group

,introduced successively one to

five atoms o f bromine . The disinfectant powers o f these com

pounds for staphylococci and streptococci increased until three

DIS INFECTAN TS '

289

atoms were reached , remained constant for the fourth , and diminished with ‘ the addition of the fifth . For B . coli they found thatthe maximum efficiency was reached with the second bromineatom .

In 1910, working with a phenyl group , the author was able to

ra i se the germicidal efficiency for B . typhosus 20 per cent . by the

incorporation of a small amount of chlorine , and 60 per cent . bysaturation .

The action of germicidal agents increases with duration of con

tact , and also with increase of concentration . Working with

anthrax spores and carbolic acid , Koch showed that in order to

produce sterility,it was necessary to employ a 1 per cent . solution

of the disinfectant for seven days , a 4 per cent . solution for threedays

,and a 5 per cent . solution for two days .

In 1889 Fraenkel and Henle drew attention to the fact that the

higher homologues of phenol contained in the creolins of those daysare more powerful germicides , and , being much more insoluble , are

less toxic than phenol . Fraenkel and B ehring at this time tested

various disinfectants,using Koch ’s silk threads impregnated with

anthrax spores ; but after removing the threads fr om the disinfectant fluids , they transferred them to peptone bouillon , instead of

solid media , as Koch had done .

In 1897 Kronig and Paul used ,instead Of threads , small sterile

B ohemian garnets of uniform size , which they shook in the emulsion

of anthrax bacilli or spores , staphylococci , etc . From time to time

a definite number were taken out,and after the disinfectant had

been removed by washing , these were well shaken in a measuredquantity of water to remove the spores ; a fractional am ount of

the washings was plated , and the number of germ inating spores

counted .

In 1907 Madsen and Nyrnan confirmed Kronig and Paul’s work ,

and also the conclusion that had already been drawn from their

figures by Ikeda— v iz that the disinfection of anthrax spores pro

ceeded after the manner of a unimolecular chemical reaction , in

which the velocity o f chemical change at any instant is propor

tional to the active mass of reacting substance present at that

instant . If for concentration (mass of reacting substance ) there be

I 9


substituted number of survivi ng spores , the unimolecular reactionequation

becomes

They showed that the disinfection of anthrax spores by heat conform ed to the same equation .

Reichert in 1909 showed that heat - coagulated serum absorbed

phenol from aqueous solution in am ount directly proportional to

concentration . He demonstrated further that the addition of a

neutral salt like sodium chloride increased both the quantity of

phenol absorbed and its germicidal power .

Cooper, in 1912 , proved that egg albumin and gelatin absorbphenol and metacresol according to the partition law ; and that

when a certain phenol concentration is reached, the proteins are

precipitated , whereby they take on a greatly increased capacity

for absorbing phenol . The precipitation of gelatin by phenol isreversible , and that of egg albumin irreversible . Certain po lypeptides are not precipitated by strong solutions of phenol . Cresols

precipitate proteins in lower concentrations than phenol . The

absorption of cresols and phenol by proteins is about the same .

It appears that the inclusion in the benzene ring of the radical

methyl (CH3 ) increases both protein -precipitating and germ icidalpowers

,but produces no change in the initial absorption of phenol

by protein ; hence it i s argued that selective germ i cidal action isdetermined by the phenol- concentration at which particular proteins are precipitated

,and that the disinfectant action of phenol i s

a mechanism similar to that Of heat .Watery solutions of antiseptics and disinfectants are more

powerful than alcoholi c,ethereal , and other solutions in which

electri cal dissociation is feeble . Koch showed that anthrax spores

are not destroyed by 5 per cent . phenol in o il in 100 days , nor by

the same percentage in alcohol in 70 days , whilst 5 per cent . con

centration in water kills in 48 . hours . These remarks apply to

iodine,thymol

,salicyli c acid , and other bodies .

Gaseous disinfectants,such as chlorine , formaldehyde , etc . ,


smaller electro - chemical dissociation , wherein fewer ions areliberated .

Soda , potash , and ammonia are germicidal in proportion to theconcentration of the OH ions .

Whilst the addit ion o f certain substances hinders the action of

certain disinfectants by modification of dissociation,in other cases

disinfectant action is assisted by such addit ions .

Phenol appears to act in disinfection as a molecule and not as anion ; phenylate of sodium , which is readilv dissociated ,

has a much

less germicidal value than phenol .When a reaction takes place in a heterogeneous system

,certain

changes other than purely chemical occur . Since the reacting

bodies are not uniform ly distributed , one is compelled to travel a

certain distance to come into contact with the other ; diffusion is

therefore a preliminary stage of the reaction . At the interfaces

where the phases are in contact , there is an accumulation of surface energy . It is known that chemical and other forms of changewill take the form of increase of concentration at a surface when

the potential of any form of energy at that surface can be dimin

ished by the change . This concentrat ion of bodies on the surfacesof contact between the phases of heterogeneous systems where suchpotential is diminished is known as adsorpt ion .

’

If at this stage no purely chemical reaction occurs , the process

stops ; but if chemical reaction takes place , its velocity in consonance

with the law of mass action is a function of the amount adsorbed ,

and is much greater than if no surface condensation had taken

place . Adsorption undoubtedly plays a large part in many forms

of disinfection , and confers upon emulsions as contrasted with solu

tions considerable advantages .

Bacteria present an enormous surface development . I f , then ,.we place in contact an emulsion of bacteria and a solution of an

antiseptic,the dissolved substance will tend to concentrate on the

surface of the bacteria more or less strongly according to their

individual nature .

We know that the same substance is a better germ icide in aqueous

solution than in alcoholic ; we also know that adsorption phenomena

are much more intense in aqueous than in alcoholic solution .

Those organic radicals which possess large germ icidal powers ,

DIS INFECTAN TS 93

such as phenyl,naphthyl

,etc Influence adsorption

,

largely ; whilst

other radicals which are destitute of germicidal action , such as

certain sulpho - compounds , are but little adsorbed .

But ionization and adsorption do not represent the whole of the

phenomena of disinfection . True chemical act ion must supplement these preliminary stages . The disinfectant agent is not

always an electrolyte . Colloidal metals are powerful disinfectants .

It has been shown that a 1 in solution of colloidal silver

sterilizes pneumococci and about equal results have been obtainedfor this reagent with B . typhosus , B . coli , and dysentery bacilli .

Charrin has shown that of two lots ofwhite mice inoculated withpneumococci

,one

,treated with isotonic colloidal silver of small

grains , survived infection ; whilst the other, retained as a control ,died in thirty hours . Colloidal silver according to this observer,is a much more powerful bactericide than salts of mercury , and is

relatively non - toxic . Colloidal mercury has been shown to possess

a greater germicidal p ower than mercuric chloride . In these casesionization has no part .

'

The last phase in the disinfectant act ion of certain bodies (Cl ,ozone , is an oxidation of living protoplasm , which , in some

cases , may proceed to complete combustion . In many instances

we cannot trace the action further than a precipitation of the protoplasm of the bacterial cell .Traces of disinfectants are frequently effective ; one cannot but

connect this fact with another— v iz . ,that in studying adsorption

curves we see the partition between adsorbent and solvent takeplace in such manner

,that with minimum concentrations the

dissolved substance is almost completely adsorbed . As Rochaix

points out , this explains why‘ an internal antiseptic acts in the

tissues despite the great dilut ion produced by their fluids .Mere inhibition o f development is not clearly expli cable unless

we invoke the intervention of adsorption phenomena .

From experimental work done , it is now j ustifiable to conclude

that in the process of disinfection one o r more of three types ofactivity may be engaged:( I ) Ionization with diffusion ; ads orption ; (3 ) purely chemical action . Further, it may be concluded

that the last type is usually preceded by the first and second in

case the disinfectant is an electrolyte,and by the second when the


disinfectant i s a colloid , and that the preliminary activ ities arenecessarv to the final action .

In organic compounds oxygen causes in general an increase in

velocity o f reaction , and tends to overcome the inertia of carbon .

The linkage of carbon to carbon is loosened by the presence ofoxygen , as specially seen in the fact that all carbon chains in combustion in oxygen break up into unlinked carbon dioxide . Special

explosive linkages are CE C, O— O, and O— Cl .

Hydrogen peroxide as an oxidizing agent is interesting in thatits mode of action appears to be very similar to that obtaining in

a number of auto - oxidations occurring in the living body . Traube

conceives that in auto - oxidations super- oxides are formed by the

action of oxygen carriers on molecular oxygen , and that ionization

of molecular oxygen does not necessarily take place as asserted by

SchOnbein .

Normally saturated fatty acids in the body undergo oxidation inthe 3 position:butyric acid becomes aceto - acetic . H

202produces

the same change:CH3

. CH2

. CH2

. COOH CH3

. CO. CH2. COOH .

Glucose is oxidized in the tissues to glycuronic acid:H202effects

the same reaction

H . OH . CHOH . CHOH . CHOH . CHOH . CHO

CHOH . CHOH . CHOH . C .HOH CHO .

Indol is oxidized to indoxyl:H202 brings about the same reac

t ion

And so with other reactions .

Such similarity of action is not only interesting from an academicpoint of view,

but also from the practical , as when a mild antisepti cfor use in the human subj ect 18 to be selected .

Hydrogen peroxide is prepared by acting on a peroxide of an

alkaline earth by an acid ,and other means

BaO2H2804 H

202BaSO4 .


In the so - called ch loride oflime (a mixture of CaCl2 and Ca (OCl)2)and other hypochlorites

,such as chlo ro s , Hermite solut ion , et c . ,

this halogen i s used in considerable quant it ies . Its action in allthese cases is that of an oxidizer .

Chloride of lime , o r bleaching powder,i s produced by passing

chlorine over moist lime , and is preferred to the soda and potashcompounds in that it can be kept as a dry powder . The hypo

chlorite portion is strongly alkaline,and in the presence ofmoisture

reacts with the CO2o f the air to form hypochlorous acid and

calcium carbonate

Ca (OCl)2 H20 CO2 CaCO

32HClO.

In the act of disinfection , the HClO splits into HCl and nascent 0 .

One part o f fresh bleaching powder to ten parts of water has beenrecommended as a disinfectantsolut ion for genera l work , and 1 partto 100 of water as a solut ion for the hands .

When solutions of chlorides o f the alkalies or alkaline earths areelectrolyzed , hypochlorous acid and the corresponding hydrate areformed

MgCl2 2HzO Mg (OH )2 2HOCl .

Herm ite applied this preparat ion to sanitation .

Chlorine and hypochlorites fai l as disinfectants when used formaterials rich in dead organic matter . Whilst the dead matter isbeing oxidized , the germ s escape .

Estimation of Cl i n Bleaching Powder .—Prepare a decinormal

solution o f sodium thiosulphate , Na2S2O3 ,5H20 . Dissolve 24

-827

grammes o f the crystals in a litre of H20 .

Weigh a gramme of bleaching powder, and grind it thoroughly in

a mortar . Add small quantities o f water at a t ime , and rub into asmooth cream . Decant the liquor into a litre flask . Cont inue togrind the sediment with successive quantit ies o f water until thewhole is transferred to the litre flask as a fine emulsion . Make up

to the mark .

Take 20 c . c . of the uniform emulsion in a basin ; add excess o f

KI solution,dilute slightly

,and acidify with aceti c acid . Titrat e

the liberated I with f ig thiosulphate and starch .

One c . c thiosulphate : 0 -0035-

4 gramme Cl .

DISINFECTAN TS 297

Another method:Prepare I and solution o f alkalinea rsenite .

Mix commercial resublimed iodine with half its weight KI , andd issolve in half its weight of water . Precipitate the I with water ,a nd filter through asbestos ; wash well to remove KI , and dry over

HzSO4 . Sublime between two large watch - glasses twice , and

finally weigh out 127 grammes . Dissolve this in 18 grammes KI

(pure) and about 250 c .c . HZO . Make up to a litre.

Dissolve grammes pure sublimed and powdered [515203 with

20 grammes pure sodium carbonate in about 250 c . c . HzO . Warm

and shake occasionally until solution is complete ; cool and make

up to a litre .

Take 20 c . c . of the well - shaken turbid emulsion of bleachingp owder in a basin ,

and run in from a burette fir arsenious solution

in slight excess '

(a drop fails to produce a blue stain on KI —Starch

paper) . Add some starch and run in rN

cI from another burette

until a slight blue colour remains . The number of c .c . $6 I requi red

g ives the number of c .c . of arsenious solution that have been addedin excess ; subtract this from the total added to obtain the numbero f c . c . of

133arsenious solution equivalent to the C1 in the bleaching

p owde’

r used

One c .c arsenious solut ion : 0 -00354 gramme available Cl .

These " methods determine quantitatively chlorinated soda ,H ermite solution , chlorine bromine and iodine -water .

Sulphur Dioxide in Solution , and in Sulphite— Estimati on in

Soluti on .-Weigh the solution (previously cooled to 5

°C . in a

freezing mixture ) in a stoppered flask ; introduce it into a seconds toppered flask , containing excess _

N_ iodine . Shake thoroughly ,1 0

a nd estimate the unchanged iodine with1316thiosulphate and

s tarch802 1

2 2H20 I1

2804 2HI .

Each c . c . ofTN

gI taking part in the reaction : 0 -0032 gramme SOz.

Estimation in Sulphite .— Powder some sulphite finely . Weigh a

small quantity in a watch - glass,and introduce it immediately into

a m easured excess of fit I in a beaker . St ir unt il the reaction i scomplete , a

‘

result only slowly obtained with insoluble sulphites

298 PRACTICAL SAN ITARY SCIENCE

e .g . , calcium sulphite . Estimate the excess iodine . It is well todo a second determ ination , using only a slight excess of 133 I .

The $02i s calculated as above .

Bromine acts in a similarmanner to chlorine by liberating nascent

oxygen . Its germicidal power in the free state has been estimatedas about equal to that of chlorine , but in combination with organicradicals it is superior . I f careful comparative tests be made

, how

ever , it will be found that bromine is a more energeti c disinfectant

than chlorine , and more energeti c than can be accounted for bythe amount of nascent O liberated . This fact leads to the conclusionthat B r acts as a disinfectant in a manner other than by liberatingoxygen .

Iodine as an oxidizer is feebler than chlorine or bromine , but

destroys bacteria more energetically than either by combining withtheir protoplasm .

Matthews found that a solution of iodine in iodide of potassiumo f a strength o f 1 in killed an emulsion of Staphylococcus

pyogenes aureus in water in fifteen seconds , whilst iodoform in fulldose was without action .

Permang anate of potassium ,K20,Mn

207 ,when acidified

with H S04 , can yield 5 atoms o f oxygen to organic matter

K O Mn207 3H2804 K

2804 2MnSO4 3H20 50 .

I f insufficient HzSO4 be used , only 3 atoms of O are furnished:

K 0,a 07H2SO

4 3H20 KZSO4 2Mn (OH)4 30 .

Like the other oxidizing disinfectants,its germicidal powers are

expended on dead organic matter and inorganic compounds , such as

sulphuretted hydrogen,ferrous salts

,nitrites

,etc rather than on

living bacteria . But for naked bacteria permanganates are power

ful disinfectants . The disinfectant activities of oxidizers are in

creased by the addition of haloid acids .Estimation of Potassium Permanganate .

-Prepare {if oxali c acidby dissolving grammes pure crystals in a litre ofwater .On adding potassium permanganate to a warm solution o f oxalic

acid and sulphuric acid,the following reaction occurs:

5H2C204 ,2H

20 3H2SO4 2KMnO4

I OCO2 K250,1

2MnSO4

18H20 .


copper , and receiving the products in water . The formalin of com

merce is a 40 per cent . solut ion o f the aldehvde in water and methylalcohol . On evaporating this solut ion i n vacuo in the presence of a

small amount of HgSO4 , a crystalline white powder falls out, of

undetermined molecular weight (CHgO) and known by the names

paraformaldehyde and paraform .

’

This polymer is volatilizedon heating into formaldehyde . Both the liquid and solid forms areused in disinfection . An enormous amount of work has been doneon the properties of formaldehyde as a germicide , and everyone is

agreed that as such it holds a high position . For application to

rooms the solution may be heated , o r the solid may be volati lized

over a lamp . There can be little doubt that the interaction between

formaldehyde and the protoplasm o f the germ is of the nature o f a

coagulation . Its powerful reducing properties remove oxygen fromthe protoplasm , probably both from hydroxyl groups and from the

oxygen united directly to carbon .

It is used for the floors,walls and ceilings of rooms as a spray ,

in the form of vapour produced by an autoclave under pressure , andas the vapour of paraform produced by a lamp . For spray work

various strengths of solution have been recommended ,ranging from

0 -

5 per cent . to per cent . and higher . Some suggest supplem enting the Spray with vapour , more especially where rooms are

exceptionally dirty, and unknown organisms like that o f smallpoxare being dealt with . In the present state of practical disinfectiona wide margin of safety should be insisted on . It is possible that

in some circumstances the highest concentration recommended failsto sterilize .

Estimati on of Formaldehyde — Form aldehyde Slowly absorbs ammonia to form hexamethylene - tetramine ; 180 parts formaldehydereact with 68 of ammonia

6CH 0 4NH3 (CH2)6N46H2

0 .

Place 10 c . c . of the solution to be tested in a flask,and neutralize ,

if necessary , with figNaOH ; dilute with water , and treat with an

excess of standard ammonia solution . It is well to stand over

night . Distil the excess of ammonia by a current of steam into

standard acid . Calculate the percentage amount of form aldehydefrom the amount o f ammonia combined .

DIS INFECTAN TS 30 1

The success which attended the early application of Carbolic Acid

as an antiseptic by Pasteur, Li ster, and others , attracted attentionto coal tars as a source of germ icides .

By suitable fractional distillation these tars can be separated

into - ( I ) First runnings (2 ) light oils ; (3 ) , heavy oils ; (4) anthracene

Oils .

Carbolic acid is contained for the most part in the light o il

fraction ; whereas the heavy o il fraction contains its homologues ,especially the cresols .At first acid and alkaline solutions of crude carbolic acid were

used as disinfectants , but it was soon found that these were not

suitable . Pure watery solutions of cresols were then tried , and

likewise abandoned for sapon ified emulsions . It was discovered

that emulsions conferred increased germicidal efficiency on the

various active phenolic bodies used , and that side - chain substitution

in the benzene ring produced the same result .

It was also discovered that metacresol,the least soluble in water,

had a higher germ i cidal power in emulsion than ortho or para

cresol .

The relative solubilitieso f the three isomers in water are

Two important stages in the evolution of coal - tar disinfectantshad now been reached and passed . The emulsion was better than

the solution:insolubility in water was o f advantage in the samedirection .

The high germicidal properties of thymol i llustrate these princi

ples, containing as it does three side - chains attached to the benzenering:

/CH3 ( 1 )C6H3— C

3H7 (4)

\OH (3 )

Its molecular weight is much higher than that ofphenolIts so lubility in water is about I in as against 1 in 15 for

phenol . Koch found that the same germicidal work was performed


on anthrax bacilli by thymol in dilution of I in as byphenol in I in

Estimation of Phenols .—The following method is based on the

precipitation o f phenol from its aqueous or alcoholic solution bybromine as tribromphenol .Prepare a standard solution consisting of 2-04 grammes sodium

bromate and 8-00 grammes potassium bromide in a litre ofwater .

One c . c . of this solution 00 012638 gramme phenol .5KBr NaB rO

3 6HC1= 5KC1+ NaCl 3Erz 3H20 .

C6H50H 3Erz C

GHZOHBr

3 3HBr .

’

ZKI Erz

2KBr + 12.

I2Na

282OJ Na25406 ZNaI .

Weigh out a gramme or two of the phenol to be tested in a tared

watch - glass , and dissolve in excess o f NaOH . Make up to , say ,

500 c . c . Take 20 c .c . (one- twenty -fifth Of the whole ) in a 300 c .c .stoppered flask , and add 25 c .c . of the standard bromide bromate

solution . In a second 300 c . c . stoppered flask place 25 c .c . of the

standard bromide bromate solution .

To each add 5 c . c . pure HCl and shake . Add such a furthermeasured quantity o f the standard bromide bromate solution to the

phenol flask that , on shaking, the white tribromphenol is left dis

tinctly yel low (excess Br) . Shake well and stand for fifteen minutes .

Add excess KI to both flasks,and titrate with a solution of thio

sulphate of Na ( say 10 grammes to a litre) .

Example — 2 168 grammes phenol required 75 c .c . standard

bromide bromate to become yellow . The iodine which the free

bromine liberated required 168 c .c . thiosulphate . But 25 c .c .bromide bromate in second flask required 518 c . c . thiosulphate .

Therefore 16-8 c . c . thiosulphate = 8~18 c . c . bromide bromate solu

tion . Therefore 75 —8-I 8= 66-82 c . c . bromide bromate solution

which interacted with phenol . Therefore x 252 -1 1 1 grammes phenol .

2 -168 2 -1 1 1 100 974

That is , this sample contains 97 4 per cent . pure phenol .

Laubenheim er showed that a 1 per cent . solution of phenol

required ninety minutes to kill a quantity of staphylococci , whereas


the most intense action , and the ortho with the lowest boilingpoint , the least intense action .

Working with higher phenols, Sommerville found that the same

principle obtains . Using the Rideal -Walker method o f est imatinggermicidal efficiency , and emulsionizing fractions from the samedist illate of blast - furnace phenylo ids , he found that a fraction boilingat 248

° possessed a coeffi cient three points above that o f another

fract ion boiling at and fiv e points above that of a thirdfract ion boiling at 207

°

Again , it is possible to alter by several points the coefficient of apheny lo id bv varying the chemical o r physical characters of theemulsion .

Changes which make for increased adsorption raise (within limits)the coefficient . Increased viscosity in the emulsion lowers (withinlimits ) the coefficient .

I f a liquid is contained between two parallel plates , and one of

these be moved w ith a constant velocity in its own plane , a certain

force is required which depends on the velocity ,the surface , and

distance , o f the two plates , and on the temperature and nature o f

the liquid . The force required to move a plate of unit surface

separated from another plate of the same size by a layer o f liquid

o funit thickness at unit velocity is known as the viscosity coefficient .Colloidal solutions may be divided into two classes if the increase

o f viscosity compared with that o f the continuous phase ( solvent )be made the basis of classification . One class presents a viscosityonly slightly higher than that of water (metal and sulphide solu

tions ) . The other, the organic colloids (albumin , gelatin ) presents

a marked increase of viscosity . In those solutions presenting a low

v iscosity,the disperse phase is present as solid particles ; in those

with high viscosity , the disperse phase is liquid . Albumin solu

tions consist of a dilute solution of albumin . in which are dispersed

globules o f a more concentrated solution . Systems of solid parti cles

o f microscopic size distributed in a liquid are known as suspen

sions those consisting of two liquid phases are known as emul

sions .

’

The part i cles in a solution , i f sufficient ly small, are in constantmotion

,oscillat ing round a central position , and also undergoing

an Irregular translatory motion . Svedberg showed that the ampli

DI S INFECTAN TS 05

tude of the motion of a particle is directly proportional to the period ,

and inv ersely'

proportional to the viscosity , of the liquid . Perrin

Showed that this B rownian movement conformed to the principlesof the kineti c theory , and that the particles could be treated aslarge molecules . The stability of the solution is intimately connected with the electric charge . The charge can be altered by theaddition of electrolytes

,and may fall to zero with suitable con

centrations , in which last case the solutions precipitate . It has

been long known that the speed of settling of such suspensions can

be increased by the addition of electrolytes .

In systems of two liquid phases , it can be shown that very small

liquid particles approaching ultramicroscopic dimensions possessa high degree -

o i rigidity . Systems of two liquid phases possessing

few and widely s eparated particles differ in no important respect

from systems containing rigid particles ; but an important differenceappears as the amount of disperse phase per unit volume increases .In

‘ the case of rigid:spherical particles in contact , the disperse phase

may -reach a maximum of 74 per cent . of the total volume . If the

disperse phase be liquid , the globules may no t merely touch one

another, but become flattened at the po ints of contact , from whichcircumstance it is obvious that there is no limit to the ratiov o l . of disperse phase

total vol .not possible to prepare emulsions containing such percentages

'

of

disperse phase unless the continuous phase is a solution of certain

substances,such as soap . Such bodies froth ,

an indication that

the dissolved substance lowers the surface tension of the solvent ;

The process of emulsification is intimately connected with suchlowering of surface tension

,or, rather, interfacial tension between the

two phases .

The stability of, emulsions (varies considerably . They are

destroyed by the addition of all substances which destroy the

emulsifying.

agent ; th’

us,’

emulsions made with soap solution are

destroyed by the‘

addition of an acid which decomposes the soap?In the making of an emulsion , the two phases are shaken up until

the disperse phase is sufficiently finely distributed . In the case ofgelatin emulsions and soap emulsions , the behaviour of the solution

?

i s not-to be explained unless by assuming that it is a system of two

20

which ratio m ay approach unity . It is


fluid phases ; in other words, it consists o f globules having a high

gelatin content in a continuous phase which is a dilute solution o f

gelatin . The solvent here may be Shifted most readily from one

phase to the other. Different behaviour i s shown by the albumins .

Egg albumin is soluble in water, and does not form a gel . eitherby cooling or concentration , but . it coagulates irrev ersiblv at a

temperature of about 60° C . The temperature o f coagulation can

be changed by adding salts , and may be raised to over 100° by

the addition of a thiocyanate . In relation to this phenomenon is

the change which follows the addition of alkali salts in the cold

the coagulation known as salting out.

’

I f at the boundary surface between the phases of a disperse

system a change in the concentration of either phase will lead to a

decrease of surface tension , this change will o ccur . The change in

concentration is adsorption . It requires work to make or enlarge

a surface ; when such surface is made , it i s the seat of energy . As

we have seen above , adsorption plays probably an important rOlein disinfection . Soap emulsions of coal- tar phenylo ids can be con

structed which are eminently suitable for the production of thisphenomenon . Such emulsions when compared with suspensions

Show a decreased Size of parti cle with reduced velocity of settlement ,increased B rownian movement with increased electri c charge , due to

the great increase o f specific surface . These emulsions provide for

a high degree of bombardment of the microbe by the active par

ticles of disinfectant , followed by marked adsorption , both necessary

prelim inaries to the final chemical action required to kill the

organism .

In most of the modern better- class disinfectants disti lled from

tar,and emulsionized in soaps

,the active principles are phenyloids .

In the raw materials these bodies are mixed with neutral o i ls ,saturated paraffins, unsaturated paraffins (olefines , pyridines

,

and a mass ofheterogeneous substances .

The unsaturated hydrocarbons are washed out with HzSO4 , and

the phenylo ids with NaOH ( formation of sodium phenylates) .

Separation i s made in laboratory practice in separator funnels .The addition of a few drops of alcohol sometimes assists the separa

tion .

Sodium phenylates are split with HZSO and the free phenyloids

308 PRACTICAL SAN ITARY S CIENCE

meat , 20 grammes o f Witte ’s peptone, 10 grammes o f sodium

chloride , and 1 l itre o f dist illed water . This mixture is boiledfor thirty minutes , filtered , and neutralized with normal sodiumhydrate , using phenolphthalein as indicator . To avoid contam inating the broth with phenolphthalein , a small aliquot part,

'

sayIO c .c . , should be taken out and titrated with "fir NaOH ; from theresult obtained a calculation is made of the amount of normal

sodium hydrate necessary for the neutralizat ion o f the remainder

o f the broth . When quite neutral , 15 c .c . of N .HCl is added . The

broth is then made up to a litre and sterilized . Where 2 o r 3 li tresare prepared at one time , as is customary , the broth is distributed

i n 500 c . c . flasks on the following day and again sterilized . With

the aid of a small separating funnel , 5 c .c . are then run into sterile

test - tubes , which , after plugging with sterile cotton -wool,are placed

in the steam sterilizer fo r half an hour .As carbolic acid crystals are frequent ly contaminated by cresols

to such an extent as to make them unreliable for'

purposes'

o

'

f

bacteriological control , their purity should be established by a

determinat ion of the solidifying- point on at least 50 c .c . ofmaterialwith the thermometer in the liquid . The point is very Sharp , the

thermometer showing a constant temperature for a period of from

five to ten minutes . The solidifying - point of the crystals is 405 ,

but anything over 40 may be accepted . A 50 per cent . by weightstock solution is then prepared and standardized by titration with

decinormal bromine . From this solution , which keeps indefinitelyin stoppered bottles

,the various working strengths are made by

diluting a comparatively large quantity, such as 100 c .c . ,to the

desired volume ; this serves to eliminate the error introduced bymeasuring out small quant ities of strong acid .

In preparing dilutions o f the disinfectant , a stock solution o r

emulsion should be prepared in a I OO c .c . stoppered cylinder with

sterilized disti lled water— 10 per cent . if the coefficient be under I ',and 1 per cent . i f over 1 . Ten c . c . o f this stock are used in preparingeach of the four dilutions required for the test . Thus, working with

a sample having a coefficient under 1 , i f it i s desired to prepare a

d ilution 1 in 70 , 10 c . c . of the 10 per cent . stock Solution are diluted

with 60 c .c . ofdist i lled water ; and in the case o f a preparation havinga coefficient over 1 , where the dilution required is 1 in 700, 10 c . c .

DIS INFECTAN TS 09

O f the 1 per cent . stock solution should be diluted with 60 c .c .

water .4

The culture o f B . typhosus i s incubated for twenty- four hours at

37°C. in Rideal -Walker broth . It is advisable to make a sub

culture every twenty - four hours from the previous twenty - four'hour culture

,even if on many days no test is performed ; but , as this

tends to attenuate the organism , it should be continued for not

longer than one month , when a fresh subculture in bro th should be

taken from an agar culture one month o ld . This procedure secures

a test culture varying but little from day to day in resistance Offered

to disinfectants,and renders the selection of the appropriate dilution

of carbolic acid easier than if the culture from which the twenty - four

hour growth is obtained were older on one occasion than on another .

The apparatus required consists of a test - tube rack, an inoculating

needle , test - tubes , and a dropping pipette . The test - tube rack

possesses two tiers,th e upper having holes for thirty test - tubes in

two rows , each row containing three sets of five . The upper tier

holds sterilized broth tubes , each ofwhich is numbered with a grease

pencil . The lower tier holds the medication- tubes,four containing

the postulant disinfectant dilutions , and one the carboli c acid con

trol dilution . . This tier is provided with a copper water-bath

intended to preserve the temperature of medication within the

prescribed limits ( 15°C . to 18

°The test - tubes are numbered

in rotation; and it'will be seen that the first medication- tube is

used for inoculat ing broth - tubes— I , 6, I I , 16, 21 , and 26 ; the

seCond'

fOr inoculating , 2 , 7 , 12 , I 7, 22 , and 27 , etc .

The needle recommended is a thin aluminium rod carrying-

a

short piece of platinum wire , 0 -018 inch in diameter (26US . gauge) ,passed through and twisted round an eye in the end of the rod .

A loop 3 millimetres interna l diameter is formed on the end of thewire . The length of the wire to the end of the loop should be aboutme inches . A fairly uniform drOp can be obtained after a little

practice by dipping the needle in the -medicated culture,and bring

ing it out with a slight j erk .

The test - tubes Should be of strong glass , so as to minimize thefisk of breakage , and l ipped to facilitate the manipulation of plugs .The size recommended is 5 inches by-g inch .

The cotton -wool plugs for both medication - tubes and broth- tubes


should be well made , so that they can be withdrawn and replacedwithout loss of t ime .

The dropping pipette is standardized to deliver O °I c .c . of the

broth culture per drop . It is loosely plugged at the top with cottonwool , and when not in actual use is kept in a sterile test - tube pluggedat the mouth with cotton -wool . For greater convenience

,the tube

should be passed through the centre of the plug , and fastened thereto

with wire . In addition to these , one o r two o f each of the followingare required:1 , 5 , and 10 c . c . pipettes ; 100 and 250 c .c . stoppered

cylinders , with inverted beakers , to safeguard against dust after

removal from sterilizer ; wire baskets to receive tubes for incubation

or sterilization . All pipettes and cylinders should be standardized .

B efore commencing the test , it is necessary to ascertain the car

bo lic acid control dilution which will give the desired result

life in two and a half and five minutes . This is done by running a

trial test with five dilutions of the carbolic acid only— say I in 80,

I in 90, I in 100 , I in 1 10, and 1 in 120 . Five c . c . o f the control

solution so ascertained are then pipetted into the fifth medication

tube , the other four receiving 5 c . c . of the various dilutions of thedisinfectant under test . To save time and apparatus , one pipette

can be made to do service at this stage by starting with the phenol

solution , and following on with the highest or lowest dilution of the

disinfectant,according as the coefficient is below or above 1 , rinsing

out the pipette in each case with the next dilution before measuringoff the sample for t est .

2

The plug o fthe culture - tube is now replaced by the culture pipette ,which

,as explained above , has a plug attached to it with wire ,

at such a height that,when the plug fits easily into the mouth of

the culture- tube , the point of the pipette is halfway down thebroth

,and clear of the clumps . The first of the five medication

tubes is now inoculated with five drops of the culture—al e 0-

5 c .c .

At intervals of half a minute each of the other medication - tubes isinoculated in turn . By the time the fifth tube has been inoculated ,the organism in the first will have been exposed to the action of

the disinfectant for two minutes , and after the next half-minute a

loopful of the latter is inoculated into the first broth - tube , loopsful

from the other medication - tubes being in turn inoculated into their

respective broth - tubes at the rate of one every thirty seconds . By

3 12 PRACTI CAL SAN ITARY SCIEN CE

the dilution of the disinfectant showing li fe in two and a half andfiv e minutes by the carboli c acid dilut ion , which of course mustshow the sam e result . In the present instance this ‘ figure of merit}o r Rideal -Walker coefficient , is 16-6.

To avoid annoyance and loss o f t ime caused by aerial contaminat ion o f tubes , etc . , it i s advisable to conduct the test in a room freefrom draughts ; a further safeguard is . provided by spraying o r

swabbing the floors and benches with an efficient disinfectant solu

tion . Needless to add , all pipettes , etc . , must be rigorouslysteri lized before use .

In .this , as in all other arbitrary tests , the need for stri ct observations of the conditions of the test is imperative .

B . TYPHOSUS:TWENTY- FOUR H OURs’ BROTH CULTURE Ar 3 7

°C

Tempera ture o f m ed ication 15°C . to 18° C .

T ime C ul ture exposed to Action o f Subculture s .

D i sm fectan ts ( M i nutes) .Sample . Dil utions .

48 hours 3 7°C .

Carbolicacid

R id eal-Walker co efficient

APPENDIX

FLOCK manufactured from rags,to be used In upholstery

,bedding ,

e tc. must meet the standard of cleanliness laid down by the LocalGovernment Board ’s Rag Flock Regulat ions , 191 2

— v iz .,nOt to

contain more than 30 parts chlorine per 100,000 parts flock

,the

chlorine to be removed as chlorides with distilled water at a temperature not exceeding 25

°C . from not less than 40 grammes o f a well

m ixed sample of flock .

Steep 50 grammes of a mixed sample of flock in litre o f distilled water governight . Decant the fluid on a filter

,and squeeze

out the flock thoroughly . Wash the flock with smaller quantit ieso f water ( say 100 c .c . three or four times

,squeezing out all the

water possible each t ime,and passing the washings through the

same filter . Make up the filt rate to a l i tre . Now evaporate 100 c .c .

of this 5 grammes flock ) to dryness with a small quantity o f

CaO in a platinum dish,and char the residue . When cool , extract

with 50 to 100 c .c . dist illed water and filter . Add a few drops ofpotassium chromate to the filtrate

,and run in from a burette silver

nitrate solution (used in estimation of C1 in water ) , 1 c .c . of whiche quals I milligramme Cl . Multiply the number o f c .c . used by 20to obtain parts Cl per flock .

Copper Sulphate i s used for greening peas and other vegetables:Estimati on of Copper .

—Ash I o grammes of the peas or othermaterial . Moisten the ash with concentrated HNO3 ; add water ,and boil . Make strongly alkaline with ammonia ,

and filter . I fn o blue colour , copper is absent . If blue

,transfer the fluid to a

N essler glass on a white t i le,and match the colour against weighed

small quant i t ies of copper sulphate converted into ammon i acal solut ion in the same manner .

'

,Or the copper may be deposited In the metallic state by passing

an electric current through the acid solut ion ,in a suitable apparatus

,

and weighed as Cu .

Tin in Canned Food.- See Local Government B oard Reports

o f Inspector of Foods , No . 7 ; Report of Buchannan and Schryver .

3 1 3

3 14 PRACTICAL SANITARY SCIENCE

1 . ColorimetricM ethod .—Prepare a solution of stannous chloride

containing 02 86 gramme per 100 c .c .

Prepare a solution o f d in itrodiphenylam inesulphoxide containing02 gramme in 100 c .c . {if NaOH . Mix 10 parts HNO3 (Sp . gr .

with 10 part s HNO3 (Sp . gr . Cool this mixture with ice , andadd 1 part o f thiodiphenylamine (prepared by heating diphenylamine with sulphur ) in small quant it ies at a time with constantst irring . Do not allow the temperature to rise above 5

°C and

add such small quant ities at a time that a hissing sound is hardlypercept ible when the solid comes into contact with the liquid mixture . The thiodiphenylamine dissolves at the beginning to form aclear solution o f red colour

,which

,before the whole of the amine

has been added,commences to thicken

,owing to the separat ion of

the nitro -body . After standing fo r some hours (not more thanhalf a day ) , suck off the nitro -body on an asbestos filter

,and wash

first with concentrated HNO3 , then with acid o f gradually diminished strength

,and finally with pure water . Now extract it with

hot alcohol in which it is not appreciably soluble .

Introduce I o grammes o f the food into a 700 c .c . Kj eldahl flask ;add 10 grammes of potassium sulphate and 10 c .c . concentrated .

sulphuric acid . Heat over small flame til l mixture chars and frothsAdd another 10 c .c . HgSO4 , and regulate the size of the flame sothat the H2SO4 can be boiled without loss from frothing . Heatt il l the contents o f the flask are quite white . Cool ; dilute withwater to about 100 c .c . Pass in HZS gas , and let stand in a corkedflask overnight . Warm slightly on a water-bath

,and filter off the

precipitated sulphide and Sulphur . Transfer the filter-paper containing the precipitate to a test - tube

,and boil with 5 c .c . coneen

trated HCl to dissolve the sulphide . Filter through a small conicalBuchner funnel into a wide -mouthed test - tube

,with a side - tube

near the top to connect with a pump . Suck as dry as possible , andwash with 25 c .c . concentrated HCl . Connect the wide-mouthedtest - tube with a C02 generat ing apparatus , and pass the gas througha tube which passes through a cork inserted in the mouth of the testtube

,and which reaches nearly to the surface of the liquid . The

side - tube serv es as an exit for the gas . Whilst still hot, throw intothe strongly acid liquid a strip of zinc foil 2 inches long , 05 inchwide

,and weighing about 07 5 gramme , and the stannic chloride is

reduced to stannous chloride . As soon as the last traces ofZn aredissolved

,add 2 c .c . of the reagent by pipette to the hot liquid , the

C02 passing the while . On addition of the reagent , the nitro -bodyis precipitated . On warming

,it passes again into solution in the

concentrated acid . B oil the solution for a minute or two , and diluteto 100 c .c . with cold water . Filter the dilute solution by means ofa pump from the unchanged nitro -body . The solution usually turnsviolet during filtration ; the full depth of colour is rapidly attained

3 16 PRACTI CAL SANITARY S CI EN CE

In using the apparatus,the air i s first expelled by a three -way tap

from the burette by raising the mercury bulb at tached to its lowerend . Air i s then taken in by lowering the bulb t il l the mercury fallsto the zero o f the graduated scale The tap to the absorpt ion pipette( the latter filled to a mark with 10 per cen t . KOH ) is next opened ,

and the air is driven over and drawn back several t imes till all C02is absorbed as indicated by constant level o f Hg . The differencebetween the first and last readings gives the amount o f C02 in partsper

Estimation of Formaldehyde in Meat Foods.

— See LocalGovernment B oard Food Reports , No . 9 . Schryver points ou t thatin meat foods it i s possible that the formaldehyde may be ent irelyoxidized to C02 and H20 by t issue oxidases ; that part of the formaldehyde may be polymerized to paraformaldehyde ; and thatformaldehyde may enter into chemical combination with some of theconst ituents o f the foodstuffs . He has confirmed the statementmade by Cervello and Pittin i , and by Batelli and Stern ,

that formaldehyde is destroyed by t issue oxidases .

When form aldehyde solut ion is dist illed,the distillat e contains

less aldehyde than the original solut ion,due to polymerizat ion by

heat into a non -volat ile polym er .

“

I t i s therefore not possible toest imate formaldehyde by steam dist i llat ion .

’

Schiff and Sorensen have shown that formaldehyde reacts withpro teins and amino - acids

,with formation of methylene - imino com

pounds,and that the react ion is a reversible one

,and only proceeds

to complet ion in presence o f large excess o f formaldehyde:

(NH2)CH2.COOH +c o CH,:N .CH2

.COOH +H20.

Amino - acids,owing to basic and acidic groups

,have an ampho

teric reaction ,and become acid on treatment with form aldehyde

the number o f amino -groups in combinat ion can be accordinglydetermined by t itrat ion with alkali . Conversely ,

it is possible byt it ration to estimate the amount o f formaldehyde which canenter into combinat ion with any product . Meat s contain relativ ely large quantit ies of are capable o f enteringinto chemical combination with the aldehyde . The react ion , asalready ment ioned

,will not proceed to full complet ion except in

presence o f excess o f aldehyde,owing to the reversibility.

In addit ion to these reversible compounds,formaldehyde can

combine with proteins to form relat ively stable insoluble products ,from which formaldehyde can be eliminated only by prolongedheat ing with water .

Any effect ive method for estimating formaldehyde in meat musttherefore be applicable to est imat ion o f free aldehyde , the polym erized product

,and aldehyde in combination with the meat .

APPENDIX 3 17

The violet colour obtained when milk containing formaldehydeis heated with strong Hcl in the presence o f an oxidizing agentcannot be used to detect aldehyde in meat

,as meat gives a violet

colour on warming with HCl in the absence o f the aldehyde dueto the formation o f haem atopo rphyrin from haemoglobin .

The following method is recommended:To I o c .c . of solution containing aldehyde add 2 c .c . o f a freshly

prepared and filtered I per cent . solut ion o fphenylhydrazine hydro;chloride . To this add I c .c . o f a 5 per cent . fresh potassium ferricyanide solution

,and 4 c .c ; of concentrated HCl . In the presence

o f formaldehyde a brilliant fuchsin - like colour is produced , whichreaches its full intensity after a few minutes ’ standing ,

.and keepswithout marked deterioration for several hours .

The addit ion of ferricyanide oxidizes the form aldehyde condensat ion product to a substance which is a weak base

,which forms a

scarlet hydrochloride . This,‘

on dilution ,undergoes hydrolyt ic

dissociat ion,yielding a base which can be. extracted with ether

,

toform a yellow solution . I f this latter be shaken with concentratedHCl , the base passes back into aqueous solut ion in the form of thescarlet hydrochloride . This reaction detects formalin in concent ration o f I part in It is quantitat ively best applied whenthe concentrat ion is I inFrom two standard solutions containing respect ively I in

and I in I 00 ,000,it is possible to make a series of dilut ions from

I part in'

upwards to serve as a colour scale when thereaction is quant itat ively applied .

Methylene - imino derivat ives can be readily hydro lysed \by cold

water ; with ammonia , formaldehyde forms a somewhat more stablederivat ive ; and with Witte ’s peptone , under certain conditions , aninsoluble product from which formaldehyde is only eliminated withsome difficulty .

By modification o f the above react ion formaldehyde can be detected in all such combinat ions . I f the mixture containing suchproduct be warmed after addition o f phenylhydrazine , the aldehydeafter scission combines immediately with phenylhydrazine to forma stable condensat ion product . This reaction ,

being irrev ersible ,

proceeds to completion . of the ferricyanide andHCl , the colour is developed in its full brilliancy .

In the sam e

’

m anner,by heating afteraddition o fphenylhydrazine

,

fo rmaldehyde can be detected when present in its polymerized form .

Heat I o grammes o f meat (minced) with dist illed water on aboiling -water bath fo r five minutes . Where the concentration - isI part formaldehyde in or less , I O c .c . of wat er is sufficient-J

Where the concentrations are higher,larger quantities ofwater must

be employed . To every 10 c .c . of water used add 2 c .c . o f a I percent . phenylhydrazine hydrochloride solution . Cool and filter from


the coagu lum through cotton -wool . To 12 c .c . o f the filtrate addI c .c 5 per cent . potassium ferricyanide and 4 c .c . concentrated HCl .Compare colour with standards made from the standard form alde

hyde solut ions .It has been found that in chilled beef treated by formaldehyde

the superficial fat contains dist inct quantities of formaldehyde ;muscular tissue unprotect ed by fat is more largely contaminatedthan other parts .

Grilling of meat but slightly diminishes the amount of form alde

hyde,and apparently causes the aldehyde to penetrate farther into

the interior . Boiling greatly diminishes it . Roasting gets rid o f

most of it . Sausages made from meat impregnated with form alde

hyde and cooked in the ordinary way ,retain it . A common depth

of penetrat ion into muscular tissue is 20 millimetres .

Arsenic in FOOdS .— See Reports of the Royal Commission on

Arsenical Poisoning , 1903 . Cd . 1869. Minutes of Evidence andAppendices , Vol . I I . , especially Appendices 16,

p . 183 ; 19,p . 201 ;

Estimation of Arachis Oil found as an Adulterant in OliveOIL— Saponify 5 gram mes of the sample with 25 c .c . alcoholicpotash solution (8 5 per Add that quantity of acetic acidwhich has previously been found by titration to exactly neutralize25 c .c . o f the above alcoholic potash ,

and cool the vessel in water .

Let stand for two hours . Filter off the acids on a filter -paper,

and wash them with 70 per cent . alcohol containing 1 per cent . HClDissolve the acids on the filter with about 40 c .c . boiling alcohol

(95 per Add about 10 c .c . ofwater to bring down the alcoholto about 20 per cent . ,

and cool down to room temperature . Filterafter an hour

,and wash the precipitate with 70 per cent . alcohol .

Dry the precipitate (arachidic acid ) at and weigh . As arachidic acid forms about 5 per cent . of arachis o il

,the weight o f the

o il i s readily calculated .

Baking-Powders.

— These preparations consist o f an acid andan alkaline const ituent

,and a third inert body— generally starch

intended to absorb moisture,and thereby prevent premature

chemical action . The alkaline const ituent is almost always bicarbonate of

‘

soda . The acid constituent may be ( I ) tartaric acid oran alkaline bitartrate ; (2 ) acid phosphate o f calcium ; o r 3 ) an alum .

Whilst sodium bicarbonate and tartaric acid are free from calciumsulphate

,acid calcium phosphate (used in the manufacture o f

3 20 PRACTICAL SAN ITARY SCIENCE

Approximate Atomic

AgAl

As

B a

A li tre of water saturated with air at 10°

C . dissolves c . c . Oat N .T P.

A litre of water saturated with air at 15°

C. di ssolves 6 96 c .c . Oat N .T .P

A li tre o f water saturated with air at 20° C. dissolves 6 28 c . c . Oat N .T.P

One hundred grammes ofwater at 15°

C. will dissolve the followingamounts expressed ln grammes of the salts indi cated .

BaSO4 o -ooo KB r

CaSO4 CaCl2Ba (NO3 )2 78 00 NH4BrNaHCO3 8-800 NaBr

KzSO4 9-600 SrB r2

Na2SO4 1 1 -

9oo Mg (NO3 )2KHCO3 I 8°

3OO BaBr2KNO3 2 1 °2oo Ca (NO2,)2Na2CO3 22 -000 NH4

NO3

KCl 25 3000 KINH4C1 26-

500 NaI

(NH4) 2SO4 33-200 B aI2

MgSO4 34-000 MgCl2

NaNO3 34-200 Ca I2

NaCl 36~I oo K2CO3

The following salts contain the numbers of molecules of watero f crystall ization indi cated: BaCl2,2H2O ; Na

2HPO4 ,12H2O ;

Na2S202,5H2O ; ZnSO4 ,7H2O ; FeSO4 ,7H2O ;

CuSO4 ,5H2O ; MgSO4 ,7H2O ; H2C2O4 ,2H2O ;

CuCl2,2 (NH4)2Cl ,2H2O

,NaNH4 2HPO4 ,4H O (micro

cosm1o salt) ; CaCl2,6H2O ; Na

2504, 10H2O4

; Na2B407 ,10H2

O ;(NH4) 2(SO4)2,6H2O ; MgSO4 ,K2SO4 ,6H2O .

INDEX

ACARUS dom esticus , 203farinae , 22 1

Acetyl v a lue , 195Acid ,

acetic,224 , 252 ,

2 53 , 259 , 260

benzo ic, 1 78

boracic, 1 74 , 187carbo lic, 30 1

citric, 166 , 267 , 268, 3 1 7hyp och lo rous , 296lactic, 252 ,

2 53malic, 2 53 ,

2 59, 260'

oxa lic,

“

134.

pho sphoric, 268

sa licylic, 177, 223sulphur ic, 224 , 267 , 268

sulphurous , 2 54tann ic, 2 57 , 2 58, 259tartar ic

, 259 , 267

2

v alue of fat, 192 ,

Acid ity of b eer , 253of bread , 23 1

o f m ilk , 1 55of sp irits , 264of water , 1 5 ,

16 , 95of wine ,

2 59 , 260

Actinom yco sis , 2 3 3Adams

’

s process , 1 57Ad eney

’

s process , 101

Adso rp tion , 292

Adulteration (see preserv ativ es) ofb eer , 2 54

o f bread , 23 1

o f butter , 185 ,187 ,

189of cheese , 203 , 205of cocoa , 285o f coffe e

,281

o f m ilk , 1 72

o f mustard, 269

of p epper , 2 70

o f sugar, 2 74

o f tea , 2 78

o fWin es , 259ZEcid ium b erberi dis

, 226

Air , 1 18

amm on ia in,140 , 144 , 145

ammon ium sulphid e in , 140 ,141 ,

144g145

bacter1a - 1n,146

Air , bromine in , 141

carbon d iox ide in , 133 , 134 , 13 5 ,

1 36

carbon disulp h id e 1mr 141carbon m onoxid e in , 136

ch lorine in , 14 1

compo sition o f, 1 18

hum id ity o f, 1 29 , 1 30

noxious gases in ,144

oxygen in ,1 30

o zon e in ,14 1

sew er,143

sulphur dioxide in , 140

sulphuretted hydrogen in ,140

susp ended m atter i n ,143

Album ino id (o rgan ic) amm on ia , 41 ,

42 46 81 92

Alcoho ls , 246 , 2 5 1 , 252 , 259 , 262

amyl a lcoho ls , 247butyl alcoho ls , 247d iethyl carbino l , 247estim ation o f alcoho l , 2 52

e thyl alcoho l , 247 , 2 5 1 , 252 ,2 53

isobutyl carb ino l , 247m ethyl a lcoho l , 246, 247

butyl carbino l , 247propyl alcoho ls , 247tab le , 265

Alka line p erm anganate , 44Alluv ium

'

, 3Aloes , 254Alum , 23 1

Amm on ia free water , 42Am oeba

, 69 ,

Anabaena ,

Anguillula , 7o , 237An im a l p arasites , 236

spin e , 71Ankylo stomum duod ena le 1 16

Annatto ,1 79 ,

199Antipyrin , 288

Antiseptic, 287Apjohn

’

s form ula , 1 29Arrowroo t , 220 , 221

Arsen ic, 254 , 3 1 7e stim ation o f, 255 , 256

in food s , 3 16

Ascarus lumbr ico ides, 237, 242Ascocarps , 228

322 PRACTICAL SANITARY SCIENCE

Asco spo res , 228

Asperg illus glaucus , 203 , 222, 223Atom ic w e ights , 3 20

Azo tobacte r , 1 14Babcock m e thod , 162

Bacil lus bo tul inus , 245butyr icus , 1 1 2

C011 commun is , 84 ,85 , 86 ,

87 ,88

,

9 1 , 104 , 1 1 2 , 1 17 , 146 , 181 ,

d emtrificans , 1 1 2

enteri tid1s spo rogenes , 84 ,85 , 87,

fluo rescens , 200

fluo rescens l iquefaciens , 1 1 2

John e ,182

K lebs -LOfii er,182

lact is aerogenes , 1 1 2

m al le i , 234mesen ter icus v ulgatus , 1 1 2

m ist bazil lus , 182

Moller’

s , 181

m yco ide s , 1 12

oed em atis m a lign i, 1 16

para typho sus B , 245

p rodigio sus (m icrococcus) , 5 , 89

p ro teus v ulgar is , 1 12 , 245p ro teus zenker i

,1 1 2

putrificus , 1 1 2

piyocyan eus , 89ab inow i tch , 182

radico la ,1 13

sm egma, 1 82

sub tilis , 1 1 2

suip estifer , 245tetan i , 1 16tuberculo s is , 84 , 181 , 182 , 200 ,

typho sus ,I

,84 , 85 , 89 , 1 16 182 ,

Bacter ia in a ir, 146

in butter , 2 00

in m eat, 233 , 245

in m ilk,180

Bacterial food -

po ison ing , 2454Bacteri o logica l examina tion o fw ater

2 ,6

Bacter io logy o f w ater ,83

Bagsho t sand s , 3Bak ing -

powde rs , 3 18

Barley , 209 , 2 15 , 2 16

Barom ete rs , 1 20 ,1 22

co rr ections of, 1 22Fo rtin , 1 20

H o oke’

s, 1 2 2

K ew,1 22

Baudouin ’

s test , 199Bean ,

B ech .

'

s test , 199Bee r , 250

acid ity o f, 253a lcoho l in , 25 2

alo es in , 254arsen ic m , 254b itters in . 253bo r ic acid in , 254gentian in , 254m a lt extract in , 25 3sal icy l ic acid in , 25 4sodium ch lo rid e in , 254sulphurous acid in , 254

Begg iato a alba , 10 , 7 1 , 73 , 74B e r1- b er i , 2 14Bicarbona te s . 2 1 , 66

Biro tation ra t io ,167

Bism ark brown, 53

Bitters , 253Bleach ing o f flour, 2 1 2

powd er , 296

Bo ric acid , 244 , 254Bould er clay , 3Boyle 's law , 1 19Brandy

, 26 1 , 262

Bread , 229acid ity o f, 23 1adultera tio n of, 23 1

a lum in, 23 1

ash o f, 230

compo sit1o n o f, 229s i lica in , 230

Brom in e , 298

Brown ian m o v em en t , 305 , 306

Bruchus p is i , 22 1Brucin e test . 54Bursaria gastri s , 10 , 73Butter , 184

adulteration o f, 185bacil lus ,

182

bacter ia in , 200

co lour ing m atters in ,199

compo s it io n o f, 184co tton seed o il in , 199curd in . 187fat. 187 , 189

ace tyl v alue o f, 195acid v alue of, 192

H ehner v alue o f, 193iod ine v alue o f, 193m e lting-

po int of, 190 , 194m icro scopic exam ina tio n o f,

192

phys ical p roperties o f, 190po lar ized ligh t test , 198

3 24 PRACTICAL SANITARY SCIENCE

Cup rous-ch lo r ide m ethod o f est i

. n1ating C02, 140

Cy st icercus bo v is , 236

ccllulo sm 2 36 , 240

tenuico ll i s 2 36

Daphn ia pulex , 7 1 , 74Dange rous w ater , 1 1

Decm o rma l so lut io n s ,1 2

Dem odex phy l loxdes suis , 236

D eod o ran t , 287Dew -

po in t , 128 ,1 29

D iam id o - benzo l , 53D iastase ,

15 2 , 208 , 2 50

D iatom s . 69 , 70 , 7 1 , 72

D in itrod iphenylam inesulphoxid e , 3 14D1phenylami ne test , 54D i s infectants , 287D isp erse phase , 305D istom a hepaticum , 2 36 , 24 1

lanceo latum , 2 36

D o tted v esse ls (ch ico ry) , 284Drepan ido tmn ia lanceo lata , 236

Echinococcus m ultilo cularis ,2 38

un ilocularis ,2 38

Egg (Ascarus lum brico ides) , 69(Taen ia so lium ) , 69(Tr ichocepha lus d ispar) , 69

Elder - leaf, 2 78

Emulsion s , 305 , 306

Endor ina , 72

En t ire flour , 2 14Ero s iv e w ater , 16

Esters in sp irits , 264E th ers in w ine s , 260

Euplotes charo n , 69Eustrongylus , 2 3 7

Fat (butter) , 189

(m ilk) , 152 ,153 ,

1 57Fault , 4Feh ling ’

s m ethod,1 70

Pavy m odification 1 7 1

Filaria , 2 37Filtrable v iruses , 2 34Flax , 77Flock , 3 13Flour- im pro v ers , 2 12 , 2 1 3Fo rm alin , 1 75 , 188 , 244 , 290 , 299 ,

Frankland’

s m e thod , 39Free and saline ammo nia , 4 1 , 42 , 46,

47 . 52 .8 r . 92

Fried land er ’

s bacillus , 89Fungi , 68Furfura l , 265Fusel o il , 262

Ga ses in water ,60

Gentian . 254Geo logy , 3Gin , 264G la ishe r

’

s fo rmula 129Glenod in ium , I o

Gluco se , 2 7 1 , 2 73G luten , 2 10

Go rgo n zo la cheese , 20 1

Graham flour , 2 13Greensands , 3 , 4Griess

’

s m ethod , 53 , 55 , 5 7Ground w ate r , 5

curv e , 5Gruyere ch eese , 20 1 ,

202

Haem ato spo rid ia , 239H a ir o f insect , 70H a ldan e

'

s apparatus fo r e stimatingC02» 3 1 5

m ethod fo r e st im at ing CO ,137

H ardness 1n w ater , 20 , 22 ,2 5

p erm anen t , 2 4 , 2 5 , 26 , 8 1

tempo rary , 2 4 , 2 5 , 26

to ta l , 24 , 26 ,8 1 , 92

H em p fib re,69 , 77

H em p e l’

s ga s burette ,13 1

H erm ite so lut ion ,296

H ock , 2 58

Houzeau’

s test , 142Hum an m ilk ,

149 ,153 , 154

Hum ulus lupulus ,2 5 1

Humus ,1 09 ,

1 10 , 1 1 1

H yd ra , 69Hydroch lo r ic acid in a ir , 14 1 ,

144H ydrodictyon , 73Hyd rogen peroxide in a ir , 142

as d is infectant, 294 , 295in m ilk ,

1 78

Igneous rocks , 5Infan t ’s fo ods , 205Infuso r ia , 69 , 70

In terpretation o f chem ica l ana lysiso f w ater , 79

Iodofo rm test , 2 5 1Ions , 297Iro n i n water ,

2, 34 , 82

I ro nstones , 3I soch lo rs ,

1 7

Jute , 78

Keph ir ,183

Kimm eridge clay , 3Kje ldat s m ethod

3 1 5,

Koum 1s , 183

INDEX

Lactalbum in ,15 1

Lactea l v esse ls , 284Lactic acid , 155 , 2 53Lactoglobulin , 15 1

Lactose , 149 , 152 , 167 , 2 05 , 207Laplace

’

s fo rmula , 124Lard , 2 05Lead in spir its , 262 , 3 17

in w ater , 30 , 32 , 82

Leffm ann - Beam p rocess ,162

Lem on—juice , 267Lep tom itus lacteus , 73Lias

, 3Lim e -juice , 267Lim eston e , 3Lin en 69Lo lium temulentum , 229London clay , 3Lunge and Zeckendorf

’

s estim ationof carbon dioxide ,

1 3 5

Magnesium in water, 28

Ma i ze , 209 , 2 1 7Ma lt extract , -

2 53Manganous chloride ,

64Marquardt m ethod , 261

Marsh’

s test, 2 55

'

Maximum th erm om eter 126

Meat, 253in spection , 233

paras i tes (an im al) in , 236p reserv ativ es i n

, 244 , 316tuberculosis m , 233Me lo s ira , 7 1

Merid ion , 10

Metallic impur ities in water , 261

Metaphenylene diam ine , 53 , 56

Methyl a lcoho l , 263Me thyl butyl carb ino l , 247Methylene - im ino com pounds , 244 ,

3 16

Methyl orange , 2 5Milk , 149

acidity of,1 55

Adam s’

s process , 1 57adulteration o f, 1 72

ana lysis of, 1 55annatto in , 179ash ,

164bacter ia in , 181 , 182

b enzo ic acid ,1 78

bo racic acid , 174case in

,1 50

cellular e lem ents of, 183citric acid

,166

co lo strum ,166

colouring m atters , 1 79

Milk , composition of, 149hum an

,1 53

condensed , 183cream , 163 , 184

ca lcium saccharate in , 184cane - sugar in ,

184gelatin in ,

184starch in ,

184dr ied ,

183fat, 1 52 ,

1 53 »I S7

fo rma lin,1 75

heated ,167

hum an,1 53

hyd rogen p eroxide 1 78

lacta lbum in ,1 51

lacti c acid , 1 55lactoglobulin ,

1 51

lacto se , 1 52 , 167 ,180

muco_

-

pro tein ,1 51

m ystin ,1 78

pasteur ized ,167

reaction of, 1 55Rose -Gottlieb m ethod ,

163sa licylic acid ,

1 77sod ium carbona te ,

1 78

so lids no t fat, 165sour

, 179sp ecific grav i ty ,

1 55strep tococci in , 182

to ta l so lids , 163turm eric

, 179Werner—Schm idt m ethod ,

160

Westpha l balance ,1 57

M illet, 209

Min im um therm om eter,1 26

Mon iezia expan sa , 236

Moulds, 203

Muco r mucedo , 203 , 222

Mucilage cells , 269Mustard

,269

Mustard o il,

Mycod erm a aceti, 268

Myxospo r idia , 239

N av icula, 72

N essler’

s reagen t , 42 , 57N ew red sand sto ne , 3N itrates in w ater

, 5 1 , 52 , 53 , 54, 57 ,

82

N itric acid in a ir, 14 1

organ ism s, 39

N itrites in water , 5 1 , 52 , 53 ,82

N itrobacter, 1 12

N i trogen as am id es ,204

as amm on ia, 20 5

as caseo ses, 204

(organ ic) , 39

326 PRACTICAL SANITARY SCIENCE

Nitrosom onas Europaea ,1 1 2

N itrous acid in a ir, 141

o rgam sm s , 39N orm al s o lut ion , 1 2

No stoc, 7 1

Oat, 209 , 2 17Odour o f w ate r , 8

( Enocyan in , 2 57( Estrus bov is , 2 36

Old red sand ston e , 3Oo l ite , 3Ordnance survey , 3Organ ic carbon , 39

matter in a ir, 3 1 5

in w ater, 38

n itrogen , 39Oscillato ria , 72

Oxidizab le o rgan icm atter , 47Oxid ized n itrogen , 5 1

Oxygen abso rbed from perm anganate ,

47 » 90 , 91 , 92 , 93 1 94 » 95 ,

d isso lv ed in w ater, 60 ,63 , 99 ,

I OO

Oxyuris v erm icularis ,23 7 ,

243Ozone , 295

Pandorina , 72

Parafo rm , 3 00

Param oecium , 69 , 7 1

Par asites in m ea t , 2 36 Saccharomyces e ll ipso ideus , 2 57Pasteurized m ilk , 167 Sa l icyl ic acid , 224Pav y-Feh ling m ethod ,

1 71 Sarco sporidia , 239so lution ,

2 75 Sea -water , 95Pea , 2 19 Self- registering therm om eter, 1 25Peat, 5 Sesam e o il , 199Pen icillium glaucum , 203 ,

22 2 Sew age , 1 ,2

,81 , 92 , 94 , 96

Pentastomum taen io ides , 239 effluents ,60

Pepper , 269 fungus , 9Peronospo ra , 222 Shales , 3Pettenkofer

’

s m ethod , 1 33 Shallow we l ls , 3Pheno l , 289 ,

292 , 302 Sh erry ,2 58

Phenolphthalein ,1 5 ,

65 , 66 S il ica ,29 ,

2 30

Pheno lsulphon ic acid , 57 S ilk , 76

Phenylhydrazin e hydroch lo ride , 3 17 S ix’

s therm om eter , 12 5Phenylo ids , 303 , 304 , 306 , 307 Slo e - leaf, 2 78

Phosphates in w ater , 2 7 , 28, 30 , 82 So ap s ,2 0 , 2 1

Phosphore tted hyd rogen ,142 Sodium chlo ride in b eer , 2 54

Pho sphorus compounds , 2 32 tetrath ionate , 49 , 60 ,62

Physwal exam ination of w ater , 7 th io sulphate , 49 ,

Picr ic acid , 57 So il , 105Pioph ila case i , 203 bacteria in ,

1 1 1

Plastering of w ine ,2 59 clay , 107

Pleurococcus , 70 h umus ,109

Plumbo - so lv ency ,16 , 2 7 , 9 5 lim e , 108

Po isonous m e tals in water , 30 m agnesia , 108

Po larim etry , 168

Po l ish e d rice , 2 14Po ro s ity o f so il , 106Port w in e , 2 58

Po st- tert iary depo sits , 3Po tassium sulphate in w ine

p erm anganate , 298

Po tato , 2 20

Fouche t's aero scope , 143Prim ary d epo s its , 3Pro teus vulgaris ,

89Puccin ia gram in is ,

2 2 5Purbcck m arb le , 3Putrefaction , 39

Q ua litativ e examinat ion o f air , 144

Q uass ia , 2 54

Ra in,6

Reaction o f w ater ,1 3 , 9 1 , 92 , 93

Reinsch'

s test 2 56

R elativ e hum id ity , 1 30Resin acids , 307R ice , 209R ideal-Wa lker co efficient, 3 12

m ethod , 304 , 307Riv ular ia ,

I O

Rose’

s m ethod , 263Rum

,264

Rye , 209

3 28 PRACTICAL SANITARY SCIEN CE

Vin egar,n itrogen in , 268

pho sphon c acid in,

2 68

specific grav ity o f, 268sulp huric an d in , 268

tota l so lids o f, 269

Visco sity , 304Vo lv ox , 72

Vo rtice lla , 7 1 , 72 , 75

Water ,1

aC1d 1ty o f, 1 5 ,

album ino id amm onia in , 4 1 , 4 2 ,

a lgae in ,68

, 69 , 70 , 7 1 , 72 , 73 , 79alum ina in , 2 1

anabmna in , 10 , 72

Bacillus co li in ,84 , 85 , 86 ,

87 ,88,

9 1

bacterio logical exam ination o f, 83bear

, 73b io logical exam ination o f, 2 ,

67ca lcium in

, 28

carbon d ioxid e in , 65 ,66

cha lk in, 2 7 ,

80

chem ica l exam ination o f, 2 , 12

ch lo rides in ,16 , 18

,19 , 20

, 30 ,

59 .82

chrom ium in, 36

co lour o f, 8

copp er in , 32

crystallization of, 3 1 7cycle ,

6

dangerous , 1 1

enzym es in ; 38

ero siv e action o f, 16

free and sa lin e amm on ia in , 4 1 ,

hardn ess o f, 20 , 2 2 , 24 , 2 5 , 26,

81 , 92

iron in , 2 , 34 ,82

lead in , 30 , 32 ,82

m agn esium in , 28

n itrates in , 5 1 , 52 , 53 , 54 , 57 , 82

n itr i tes in , 5 1 , 52 , 53 ,82

odour o f, 8

organ ic m atter in , 38

oxidizab le o rgan ic m atter in , 47oxygen d isso lv ed in , 60

p eaty , 5

pho sphates in , 2 7 , 28 , 30 , 82

physical exam ination o f, 2 , 7 , 9 1 ,Xyleno ls , 303

plum bo- so lv ency o f, 16 , 2 7 , 95 Z1uc 1n w ater, 36,

82

po isonous m etals in , 30 Zym ase ,249

pure, 91 Zym o lyte , 249

Ba i llze r e, Tim/a l l 69° Cox , 8 Hen r ietta S treat, Cev ent Ga rden

“fate r , ra in , 6

reaction o f, 13 , 91 , 92 , 93sed im ent , 67s ilica in , 29so lid res idue o f, 27 , 92sulphates in , 29 , 30 , 82

susp icious , 1 1

taste o f, 10

tin in , 33to tal so lids in , 92

turb id ity o f, 7who lesom e , 1 1

z inc in, 36 , 82

Weald clay , 3Wern er- Schm idt m ethod , 160 , 203Westphal ba lance , 157Wheat , 209

flour , 209ash o f, 2 1 1

compo sition o f, 2 10

fat o f, 2 10

gluten o f, 2 10

starch granules o f, 2 1 1sugar o f, 2 10w ater o f, 2 1 1

Wh isky , 261

acidi ty o f, 264a lcoho l of, 262

furfura l in , 265fuse ] o il in , 262

m etallic impurities in , 262

m ethyl a lcoho l in , 263Who lem ea l flour , 2 13VVi llow - leaf, 2 78

Wine ,2 56

acid ity o f, 2 59a lcoho l o f, 2 59ash o f, 260

co louring m atter in , 2 59e th ers of, 260extract o f, 260p lastering of, 2 59po tassium sulphate in , 260

sugars in , 260

w ater in , 2 59Winkler ’

s m e thod ,63

Witte 's p ep tone , 308

Wood ce lls , 69 , 72

Woo l , 69 , 7o , 76

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